Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
Implementing BGP
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Contents

Implementing BGP

Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-free interdomain routing between autonomous systems. An autonomous system is a set of routers under a single technical administration. Routers in an autonomous system can use multiple Interior Gateway Protocols (IGPs) to exchange routing information inside the autonomous system and an EGP to route packets outside the autonomous system.

This module provides the conceptual and configuration information for BGP on Cisco IOS XR software.


Note


For more information about BGP and complete descriptions of the BGP commands listed in this module, see Related Documents section of this module. To locate documentation for other commands that might appear while performing a configuration task, search online in the Cisco ASR 9000 Series Router software master command index.


Feature History for Implementing BGP

Release

Modification

Release 3.7.2

This feature was introduced.

Release 3.9.0

The following features were supported:

  • BGP Prefix Independent Convergence Unipath Primary Backup
  • BGP Local Label Retention
  • Asplain notation for 4-byte Autonomous System Number
  • BGP Nonstop Routing
  • Command Line Interface (CLI) consistency for BGP commands
  • L2VPN Address Family Configuration Mode

Release 4.0.0

The following features were supported:

  • BGP Add Path Advertisement
  • Accumulated iGP (AiGP)
  • Pre-route
  • IPv4 BGP-Policy Accounting
  • IPv6 uRPF

Release 4.1.0

Support for 5000 BGP NSR sessions was added

Release 4.1.1

The following features were added:
  • BGP Accept Own
  • BGP DMZ Link Bandwidth for Unequal Cost Recursive Load Balancing

Release 4.2.0

The following features were supported:

  • Selective VRF Download
  • BGP Multi-Instance/Multi-AS
  • BFD Multihop Support for BGP
  • BGP Error Handling

Support for Distributed BGP (bgp distributed speaker) configuration was removed.

Release 4.2.1

The following features were supported:
  • BGP 3107 PIC Updates for Global Prefixes
  • BGP Prefix Independent Convergence for RIB and FIB
  • BGP Prefix Origin Validation Based on RPKI

Release 4.2.3

The BGP Attribute Filtering feature was added.

Release 4.3.0

The BGP-RIB Feedback Mechanism for Update Generation feature was added

Release 4.3.1

The following features were supported
  • BGP VRF Dynamic Route Leaking

Release 4.3.2

The Per-neighbor Link Bandwidth feature was added.

Prerequisites for Implementing BGP

You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Information About Implementing BGP

To implement BGP, you need to understand the following concepts:

BGP Functional Overview

BGP uses TCP as its transport protocol. Two BGP routers form a TCP connection between one another (peer routers) and exchange messages to open and confirm the connection parameters.

BGP routers exchange network reachability information. This information is mainly an indication of the full paths (BGP autonomous system numbers) that a route should take to reach the destination network. This information helps construct a graph that shows which autonomous systems are loop free and where routing policies can be applied to enforce restrictions on routing behavior.

Any two routers forming a TCP connection to exchange BGP routing information are called peers or neighbors. BGP peers initially exchange their full BGP routing tables. After this exchange, incremental updates are sent as the routing table changes. BGP keeps a version number of the BGP table, which is the same for all of its BGP peers. The version number changes whenever BGP updates the table due to routing information changes. Keepalive packets are sent to ensure that the connection is alive between the BGP peers and notification packets are sent in response to error or special conditions.


Note


For information on configuring BGP to distribute Multiprotocol Label Switching (MPLS) Layer 3 virtual private network (VPN) information, see the Cisco ASR 9000 Series Aggregation Services Router MPLS Configuration Guide

For information on BGP support for Bidirectional Forwarding Detection (BFD), see the Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Configuration Guide and the Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Command Reference.


BGP Router Identifier

For BGP sessions between neighbors to be established, BGP must be assigned a router ID. The router ID is sent to BGP peers in the OPEN message when a BGP session is established.

BGP attempts to obtain a router ID in the following ways (in order of preference):

  • By means of the address configured using the bgp router-id command in router configuration mode.
  • By using the highest IPv4 address on a loopback interface in the system if the router is booted with saved loopback address configuration.
  • By using the primary IPv4 address of the first loopback address that gets configured if there are not any in the saved configuration.

If none of these methods for obtaining a router ID succeeds, BGP does not have a router ID and cannot establish any peering sessions with BGP neighbors. In such an instance, an error message is entered in the system log, and the show bgp summary command displays a router ID of 0.0.0.0.

After BGP has obtained a router ID, it continues to use it even if a better router ID becomes available. This usage avoids unnecessary flapping for all BGP sessions. However, if the router ID currently in use becomes invalid (because the interface goes down or its configuration is changed), BGP selects a new router ID (using the rules described) and all established peering sessions are reset.


Note


We strongly recommend that the bgp router-id command is configured to prevent unnecessary changes to the router ID (and consequent flapping of BGP sessions).


BGP Default Limits

Cisco IOS XR BGP imposes maximum limits on the number of neighbors that can be configured on the router and on the maximum number of prefixes that are accepted from a peer for a given address family. This limitation safeguards the router from resource depletion caused by misconfiguration, either locally or on the remote neighbor. The following limits apply to BGP configurations:

  • The default maximum number of peers that can be configured is 4000. The default can be changed using the bgp maximum neighbor command. The limit range is 1 to 15000. Any attempt to configure additional peers beyond the maximum limit or set the maximum limit to a number that is less than the number of peers currently configured will fail.
  • To prevent a peer from flooding BGP with advertisements, a limit is placed on the number of prefixes that are accepted from a peer for each supported address family. The default limits can be overridden through configuration of the maximum-prefix limit command for the peer for the appropriate address family. The following default limits are used if the user does not configure the maximum number of prefixes for the address family:
    • IPv4 Unicast: 1048576
    • IPv4 Multicast: 131072
    • IPv4 Labeled-unicast: 131072
    • VPNv4 Unicast: 2097152
    • IPv4 MDT: 131072
    • IPv4 Tunnel: 1048576
    • IPv6 Unicast: 524288
    • IPv6 Multicast: 131072
    • IPv6 Labeled-unicast: 131072
    • VPNv6 Unicast: 1048576
    • L2VPN EVPN: 2097152
    A cease notification message is sent to the neighbor and the peering with the neighbor is terminated when the number of prefixes received from the peer for a given address family exceeds the maximum limit (either set by default or configured by the user) for that address family. It is possible that the maximum number of prefixes for a neighbor for a given address family has been configured after the peering with the neighbor has been established and a certain number of prefixes have already been received from the neighbor for that address family. A cease notification message is sent to the neighbor and peering with the neighbor is terminated immediately after the configuration if the configured maximum number of prefixes is fewer than the number of prefixes that have already been received from the neighbor for the address family.

BGP Next Hop Tracking

BGP receives notifications from the Routing Information Base (RIB) when next-hop information changes (event-driven notifications). BGP obtains next-hop information from the RIB to:

  • Determine whether a next hop is reachable.
  • Find the fully recursed IGP metric to the next hop (used in the best-path calculation).
  • Validate the received next hops.
  • Calculate the outgoing next hops.
  • Verify the reachability and connectedness of neighbors.

BGP is notified when any of the following events occurs:

  • Next hop becomes unreachable
  • Next hop becomes reachable
  • Fully recursed IGP metric to the next hop changes
  • First hop IP address or first hop interface change
  • Next hop becomes connected
  • Next hop becomes unconnected
  • Next hop becomes a local address
  • Next hop becomes a nonlocal address

Note


Reachability and recursed metric events trigger a best-path recalculation.


Event notifications from the RIB are classified as critical and noncritical. Notifications for critical and noncritical events are sent in separate batches. However, a noncritical event is sent along with the critical events if the noncritical event is pending and there is a request to read the critical events.

  • Critical events are related to the reachability (reachable and unreachable), connectivity (connected and unconnected), and locality (local and nonlocal) of the next hops. Notifications for these events are not delayed.
  • Noncritical events include only the IGP metric changes. These events are sent at an interval of 3 seconds. A metric change event is batched and sent 3 seconds after the last one was sent.

The next-hop trigger delay for critical and noncritical events can be configured to specify a minimum batching interval for critical and noncritical events using the nexthop trigger-delay command. The trigger delay is address family dependent.

The BGP next-hop tracking feature allows you to specify that BGP routes are resolved using only next hops whose routes have the following characteristics:

  • To avoid the aggregate routes, the prefix length must be greater than a specified value.
  • The source protocol must be from a selected list, ensuring that BGP routes are not used to resolve next hops that could lead to oscillation.

This route policy filtering is possible because RIB identifies the source protocol of route that resolved a next hop as well as the mask length associated with the route. The nexthop route-policy command is used to specify the route-policy.

For information on route policy filtering for next hops using the next-hop attach point, see the Implementing Routing Policy Language on Cisco ASR 9000 Series Router module of Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide (this publication).

Scoped IPv4/VPNv4 Table Walk

To determine which address family to process, a next-hop notification is received by first dereferencing the gateway context associated with the next hop, then looking into the gateway context to determine which address families are using the gateway context. The IPv4 unicast and VPNv4 unicast address families share the same gateway context, because they are registered with the IPv4 unicast table in the RIB. As a result, both the global IPv4 unicast table and the VPNv4 table are processed when an IPv4 unicast next-hop notification is received from the RIB. A mask is maintained in the next hop, indicating whether the next hop belongs to IPv4 unicast or VPNv4 unicast, or both. This scoped table walk localizes the processing in the appropriate address family table.

Reordered Address Family Processing

The Cisco IOS XR software walks address family tables based on the numeric value of the address family. When a next-hop notification batch is received, the order of address family processing is reordered to the following order:

  • IPv4 tunnel
  • VPNv4 unicast
  • IPv4 labeled unicast
  • IPv4 unicast
  • IPv4 multicast
  • IPv6 unicast

New Thread for Next-Hop Processing

The critical-event thread in the spkr process handles only next-hop, Bidirectional Forwarding Detection (BFD), and fast-external-failover (FEF) notifications. This critical-event thread ensures that BGP convergence is not adversely impacted by other events that may take a significant amount of time.

show, clear, and debug Commands

The show bgp nexthops command provides statistical information about next-hop notifications, the amount of time spent in processing those notifications, and details about each next hop registered with the RIB. The clear bgp nexthop performance-statistics command ensures that the cumulative statistics associated with the processing part of the next-hop show command can be cleared to help in monitoring. The clear bgp nexthop registration command performs an asynchronous registration of the next hop with the RIB. See the BGP Commands on Cisco ASR 9000 Series Router module of Cisco ASR 9000 Series Aggregation Services Router Routing Command Referencefor information on the next-hop show and clear commands.

The debug bgp nexthop command displays information on next-hop processing. The out keyword provides debug information only about BGP registration of next hops with RIB. The in keyword displays debug information about next-hop notifications received from RIB. The out keyword displays debug information about next-hop notifications sent to the RIB. See the BGP Debug Commands on Cisco ASR 9000 Series Aggregation Services Router module of Cisco ASR 9000 Series Aggregation Services Router Routing Debug Command Reference.

Autonomous System Number Formats in BGP

Autonomous system numbers (ASNs) are globally unique identifiers used to identify autonomous systems (ASs) and enable ASs to exchange exterior routing information between neighboring ASs. A unique ASN is allocated to each AS for use in BGP routing. ASNs are encoded as 2-byte numbers and 4-byte numbers in BGP.

2-byte Autonomous System Number Format

The 2-byte ASNs are represented in asplain notation. The 2-byte range is 1 to 65535.

4-byte Autonomous System Number Format

To prepare for the eventual exhaustion of 2-byte Autonomous System Numbers (ASNs), BGP has the capability to support 4-byte ASNs. The 4-byte ASNs are represented both in asplain and asdot notations.

The byte range for 4-byte ASNs in asplain notation is 1-4294967295. The AS is represented as a 4-byte decimal number. The 4-byte ASN asplain representation is defined in draft-ietf-idr-as-representation-01.txt.

For 4-byte ASNs in asdot format, the 4-byte range is 1.0 to 65535.65535 and the format is:

high-order-16-bit-value-in-decimal . low-order-16-bit-value-in-decimal

The BGP 4-byte ASN capability is used to propagate 4-byte-based AS path information across BGP speakers that do not support 4-byte AS numbers. See draft-ietf-idr-as4bytes-12.txt for information on increasing the size of an ASN from 2 bytes to 4 bytes. AS is represented as a 4-byte decimal number

as-format Command

The as-format command configures the ASN notation to asdot. The default value, if the as-format command is not configured, is asplain.

BGP Configuration

BGP in Cisco IOS XR software follows a neighbor-based configuration model that requires that all configurations for a particular neighbor be grouped in one place under the neighbor configuration. Peer groups are not supported for either sharing configuration between neighbors or for sharing update messages. The concept of peer group has been replaced by a set of configuration groups to be used as templates in BGP configuration and automatically generated update groups to share update messages between neighbors.

Configuration Modes

BGP configurations are grouped into modes. The following sections show how to enter some of the BGP configuration modes. From a mode, you can enter the ? command to display the commands available in that mode.

Router Configuration Mode

The following example shows how to enter router configuration mode:

  RP/0/RSP0/CPU0:router# configuration
  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# 
  
Router Address Family Configuration Mode

The following example shows how to enter router address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 112
  RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 multicast
  RP/0/RSP0/CPU0:router(config-bgp-af)#
  
Neighbor Configuration Mode

The following example shows how to enter neighbor configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.0.1
  RP/0/RSP0/CPU0:router(config-bgp-nbr)#
  
Neighbor Address Family Configuration Mode

The following example shows how to enter neighbor address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 112
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.0.1
  RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)#
  
VRF Configuration Mode

The following example shows how to enter VPN routing and forwarding (VRF) configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_A
  RP/0/RSP0/CPU0:router(config-bgp-vrf)#
  
VRF Address Family Configuration Mode

The following example shows how to enter VRF address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 112
  RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_A
  RP/0/RSP0/CPU0:router(config-bgp-vrf)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-vrf-af)#
  
VRF Neighbor Configuration Mode

The following example shows how to enter VRF neighbor configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_A
  RP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 11.0.1.2
  RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# 
  
VRF Neighbor Address Family Configuration Mode

The following example shows how to enter VRF neighbor address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 112
  RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_A
  RP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 11.0.1.2 
  RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)#
  
VPNv4 Address Family Configuration Mode

The following example shows how to enter VPNv4 address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 152
  RP/0/RSP0/CPU0:router(config-bgp)# address-family vpnv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-af)# 
  
L2VPN Address Family Configuration Mode

The following example shows how to enter L2VPN address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 100
  RP/0/RSP0/CPU0:router(config-bgp)# address-family l2vpn vpls-vpws
  RP/0/RSP0/CPU0:router(config-bgp-af)#
  

Neighbor Submode 

Cisco IOS XR BGP uses a neighbor submode to make it possible to enter configurations without having to prefix every configuration with the neighbor keyword and the neighbor address:

  • Cisco IOS XR software has a submode available for neighbors in which it is not necessary for every command to have a “neighbor x.x.x.x” prefix: In Cisco IOS XR software, the configuration is as follows:
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.23.1.2
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 multicast
  • An address family configuration submode inside the neighbor configuration submode is available for entering address family-specific neighbor configurations. In Cisco IOS XR software, the configuration is as follows:
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 2002::2
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2023
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv6 unicast
      RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# next-hop-self
      RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy one in
  • You must enter neighbor-specific IPv4, IPv6, VPNv4, or VPNv6 commands in neighbor address-family configuration submode. In Cisco IOS XR software, the configuration is as follows:
      RP/0/RSP0/CPU0:router(config)# router bgp 109
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.40.24
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
      RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# maximum-prefix 1000
                
  • You must enter neighbor-specific IPv4 and IPv6 commands in VRF neighbor address-family configuration submode. In Cisco IOS XR software, the configuration is as follows:
      RP/0/RSP0/CPU0:router(config)# router bgp 110
      RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_A 
      RP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 11.0.1.2
      RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# address-family ipv4 unicast
      RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# route-policy pass all in
      
                

Configuration Templates

The af-group, session-group, and neighbor-group configuration commands provide template support for the neighbor configuration in Cisco IOS XR software.

The af-group command is used to group address family-specific neighbor commands within an IPv4, IPv6, or VPNv4, address family. Neighbors that have the same address family configuration are able to use the address family group (af-group) name for their address family-specific configuration. A neighbor inherits the configuration from an address family group by way of the use command. If a neighbor is configured to use an address family group, the neighbor (by default) inherits the entire configuration from the address family group. However, a neighbor does not inherit all of the configuration from the address family group if items are explicitly configured for the neighbor. The address family group configuration is entered under the BGP router configuration mode. The following example shows how to enter address family group configuration mode.

RP/0/RSP0/CPU0:router(config)# router bgp 140
RP/0/RSP0/CPU0:router(config-bgp)# af-group afmcast1 address-family ipv4 multicast
RP/0/RSP0/CPU0:router(config-bgp-afgrp)#
    

The session-group command allows you to create a session group from which neighbors can inherit address family-independent configuration. A neighbor inherits the configuration from a session group by way of the use command. If a neighbor is configured to use a session group, the neighbor (by default) inherits the entire configuration of the session group. A neighbor does not inherit all of the configuration from a session group if a configuration is done directly on that neighbor. The following example shows how to enter session group configuration mode:

  RP/0/RSP0/CPU0:router# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# session-group session1
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# 
   

The neighbor-group command helps you apply the same configuration to one or more neighbors. Neighbor groups can include session groups and address family groups and can comprise the complete configuration for a neighbor. After a neighbor group is configured, a neighbor can inherit the configuration of the group using the use command. If a neighbor is configured to use a neighbor group, the neighbor inherits the entire BGP configuration of the neighbor group.

The following example shows how to enter neighbor group configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 123
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group nbrgroup1
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)#
    

The following example shows how to enter neighbor group address family configuration mode:

  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group nbrgroup1
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)#
    
  • However, a neighbor does not inherit all of the configuration from the neighbor group if items are explicitly configured for the neighbor. In addition, some part of the configuration of the neighbor group could be hidden if a session group or address family group was also being used.

Configuration grouping has the following effects in Cisco IOS XR software:

  • Commands entered at the session group level define address family-independent commands (the same commands as in the neighbor submode).
  • Commands entered at the address family group level define address family-dependent commands for a specified address family (the same commands as in the neighbor-address family configuration submode).
  • Commands entered at the neighbor group level define address family-independent commands and address family-dependent commands for each address family (the same as all available neighbor commands), and define the use command for the address family group and session group commands.

Template Inheritance Rules

In Cisco IOS XR software, BGP neighbors or groups inherit configuration from other configuration groups.

For address family-independent configurations:

  • Neighbors can inherit from session groups and neighbor groups.
  • Neighbor groups can inherit from session groups and other neighbor groups.
  • Session groups can inherit from other session groups.
  • If a neighbor uses a session group and a neighbor group, the configurations in the session group are preferred over the global address family configurations in the neighbor group.

For address family-dependent configurations:

  • Address family groups can inherit from other address family groups.
  • Neighbor groups can inherit from address family groups and other neighbor groups.
  • Neighbors can inherit from address family groups and neighbor groups.

Configuration group inheritance rules are numbered in order of precedence as follows:

  1. If the item is configured directly on the neighbor, that value is used. In the example that follows, the advertisement interval is configured both on the neighbor group and neighbor configuration and the advertisement interval being used is from the neighbor configuration:
      RP/0/RSP0/CPU0:router(config)# router bgp 140
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.1.1.1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# advertisement-interval 20
    
    
    The following output from the show bgp neighbors command shows that the advertisement interval used is 20 seconds:
      RP/0/RSP0/CPU0:routershow bgp neighbors 10.1.1.1
      
      BGP neighbor is 10.1.1.1, remote AS 1, local AS 140, external link
       Remote router ID 0.0.0.0
        BGP state = Idle
        Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds
        Received 0 messages, 0 notifications, 0 in queue
        Sent 0 messages, 0 notifications, 0 in queue
        Minimum time between advertisement runs is 20 seconds
      
       For Address Family: IPv4 Unicast
        BGP neighbor version 0
        Update group: 0.1
        eBGP neighbor with no inbound or outbound policy; defaults to 'drop'
        Route refresh request: received 0, sent 0
        0 accepted prefixes
        Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288
        Threshold for warning message 75%
      
        Connections established 0; dropped 0
        Last reset 00:00:14, due to BGP neighbor initialized
        External BGP neighbor not directly connected.
      
  2. Otherwise, if an item is configured to be inherited from a session-group or neighbor-group and on the neighbor directly, then the configuration on the neighbor is used. If a neighbor is configured to be inherited from session-group or af-group, but no directly configured value, then the value in the session-group or af-group is used. In the example that follows, the advertisement interval is configured on a neighbor group and a session group and the advertisement interval value being used is from the session group:
      RP/0/RSP0/CPU0:router(config)# router bgp 140
      RP/0/RSP0/CPU0:router(config-bgp)# session-group AS_2
      RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15
      RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 20
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.0.1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use session-group AS_2
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1
    
    The following output from the show bgp neighbors command shows that the advertisement interval used is 15 seconds:
      RP/0/RSP0/CPU0:routershow bgp neighbors 192.168.0.1
      
      BGP neighbor is 192.168.0.1, remote AS 1, local AS 140, external link
       Remote router ID 0.0.0.0
        BGP state = Idle
        Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds
        Received 0 messages, 0 notifications, 0 in queue
        Sent 0 messages, 0 notifications, 0 in queue
        Minimum time between advertisement runs is 15 seconds
      
       For Address Family: IPv4 Unicast
        BGP neighbor version 0
        Update group: 0.1
        eBGP neighbor with no inbound or outbound policy; defaults to 'drop'
        Route refresh request: received 0, sent 0
        0 accepted prefixes
        Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288
        Threshold for warning message 75%
      
        Connections established 0; dropped 0
        Last reset 00:03:23, due to BGP neighbor initialized
        External BGP neighbor not directly connected.
      
  3. Otherwise, if the neighbor uses a neighbor group and does not use a session group or address family group, the configuration value can be obtained from the neighbor group either directly or through inheritance. In the example that follows, the advertisement interval from the neighbor group is used because it is not configured directly on the neighbor and no session group is used:
      RP/0/RSP0/CPU0:router(config)# router bgp 150
      RP/0/RSP0/CPU0:router(config-bgp)# session-group AS_2
      RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 20
      RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1
       
    The following output from the show bgp neighbors command shows that the advertisement interval used is 15 seconds:
       RP/0/RSP0/CPU0:routershow bgp neighbors 192.168.1.1
      
      BGP neighbor is 192.168.2.2, remote AS 1, local AS 140, external link
       Remote router ID 0.0.0.0
        BGP state = Idle
        Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds
        Received 0 messages, 0 notifications, 0 in queue
        Sent 0 messages, 0 notifications, 0 in queue
        Minimum time between advertisement runs is 15 seconds
      
       For Address Family: IPv4 Unicast
        BGP neighbor version 0
        Update group: 0.1
        eBGP neighbor with no outbound policy; defaults to 'drop'
        Route refresh request: received 0, sent 0
        Inbound path policy configured
        Policy for incoming advertisements is POLICY_1
        0 accepted prefixes
        Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288
        Threshold for warning message 75%
      
        Connections established 0; dropped 0
        Last reset 00:01:14, due to BGP neighbor initialized
        External BGP neighbor not directly connected.
      
    To illustrate the same rule, the following example shows how to set the advertisement interval to 15 (from the session group) and 25 (from the neighbor group). The advertisement interval set in the session group overrides the one set in the neighbor group. The inbound policy is set to POLICY_1 from the neighbor group.
      RP/0/RSP0/CPU0:routerconfig)# router bgp 140
      RP/0/RSP0/CPU0:router(config-bgp)# session-group ADV
      RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15
      RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group ADV_2
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 25
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# route-policy POLICY_1 in
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# exit
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.2.2
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use session-group ADV
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group ADV_2
      
    The following output from the show bgp neighbors command shows that the advertisement interval used is 15 seconds:
      RP/0/RSP0/CPU0:routershow bgp neighbors 192.168.2.2
      
      BGP neighbor is 192.168.2.2, remote AS 1, local AS 140, external link
       Remote router ID 0.0.0.0
        BGP state = Idle
        Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds
        Received 0 messages, 0 notifications, 0 in queue
        Sent 0 messages, 0 notifications, 0 in queue
        Minimum time between advertisement runs is 15 seconds
      
       For Address Family: IPv4 Unicast
        BGP neighbor version 0
        Update group: 0.1
        eBGP neighbor with no inbound or outbound policy; defaults to 'drop'
        Route refresh request: received 0, sent 0
        0 accepted prefixes
        Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288
        Threshold for warning message 75%
      
        Connections established 0; dropped 0
        Last reset 00:02:03, due to BGP neighbor initialized
        External BGP neighbor not directly connected.
      
  4. Otherwise, the default value is used. In the example that follows, neighbor 10.0.101.5 has the minimum time between advertisement runs set to 30 seconds (default) because the neighbor is not configured to use the neighbor configuration or the neighbor group configuration:
      RP/0/RSP0/CPU0:router(config)# router bgp 140
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# remote-as 1
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group adv_15
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# remote-as 10
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15
      RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.101.5
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# exit
      RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.101.10
      RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group adv_15
      
    The following output from the show bgp neighbors command shows that the advertisement interval used is 30 seconds:
      RP/0/RSP0/CPU0:routershow bgp neighbors 10.0.101.5
      
      BGP neighbor is 10.0.101.5, remote AS 1, local AS 140, external link
       Remote router ID 0.0.0.0
        BGP state = Idle
        Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds
        Received 0 messages, 0 notifications, 0 in queue
        Sent 0 messages, 0 notifications, 0 in queue
        Minimum time between advertisement runs is 30 seconds
      
       For Address Family: IPv4 Unicast
        BGP neighbor version 0
        Update group: 0.2
        eBGP neighbor with no inbound or outbound policy; defaults to 'drop'
        Route refresh request: received 0, sent 0
        0 accepted prefixes
        Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288
        Threshold for warning message 75%
      Connections established 0; dropped 0
        Last reset 00:00:25, due to BGP neighbor initialized
        External BGP neighbor not directly connected.
      

The inheritance rules used when groups are inheriting configuration from other groups are the same as the rules given for neighbors inheriting from groups.

Viewing Inherited Configurations

You can use the following show commands to view BGP inherited configurations:

show bgp neighbors

Use the show bgp neighbors command to display information about the BGP configuration for neighbors.

  • Use the configuration keyword to display the effective configuration for the neighbor, including any settings that have been inherited from session groups, neighbor groups, or address family groups used by this neighbor.
  • Use the inheritance keyword to display the session groups, neighbor groups, and address family groups from which this neighbor is capable of inheriting configuration.

The show bgp neighbors command examples that follow are based on this sample configuration:

  RP/0/RSP0/CPU0:router(config)# router bgp 142
  RP/0/RSP0/CPU0:router(config-bgp)# af-group GROUP_3 address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# next-hop-self
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# route-policy POLICY_1 in
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# session-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group GROUP_1
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# use session-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# ebgp-multihop 3
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# weight 100
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# send-community-ebgp
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# exit
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 multicast
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# default-originate
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# exit
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.0.1
  RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2
  RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group GROUP_1
  RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# use af-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# weight 200
  

The following example displays sample output from the show bgp neighbors command using the inheritance keyword. The example shows that the neighbor inherits session parameters from neighbor group GROUP_1, which in turn inherits from session group GROUP_2. The neighbor inherits IPv4 unicast parameters from address family group GROUP_3 and IPv4 multicast parameters from neighbor group GROUP_1:

  RP/0/RSP0/CPU0:routershow bgp neighbors 192.168.0.1 inheritance 
  
    Session:        n:GROUP_1 s:GROUP_2
    IPv4 Unicast:   a:GROUP_3
    IPv4 Multicast: n:GROUP_1
    

The following example displays sample output from the show bgp neighbors command using the configuration keyword. The example shows from where each item of configuration was inherited, or if it was configured directly on the neighbor (indicated by [ ]). For example, the ebgp-multihop 3 command was inherited from neighbor group GROUP_1 and the next-hop-self command was inherited from the address family group GROUP_3:

  RP/0/RSP0/CPU0:routershow bgp neighbors 192.168.0.1 configuration 
  
  neighbor 192.168.0.1
   remote-as 2                   []
   advertisement-interval 15     [n:GROUP_1 s:GROUP_2]
   ebgp-multihop 3               [n:GROUP_1]
   address-family ipv4 unicast   []
    next-hop-self                [a:GROUP_3]
    route-policy POLICY_1    in  [a:GROUP_3]
    weight 200                   []
   address-family ipv4 multicast [n:GROUP_1]
    default-originate            [n:GROUP_1]
  
show bgp af-group

Use the show bgp af-group command to display address family groups:

  • Use the configuration keyword to display the effective configuration for the address family group, including any settings that have been inherited from address family groups used by this address family group.
  • Use the inheritance keyword to display the address family groups from which this address family group is capable of inheriting configuration.
  • Use the users keyword to display the neighbors, neighbor groups, and address family groups that inherit configuration from this address family group.

The show bgp af-group sample commands that follow are based on this sample configuration:

  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# af-group GROUP_3 address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# remove-private-as
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# route-policy POLICY_1 in
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# af-group GROUP_1 address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# use af-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# maximum-prefix 2500 75 warning-only
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# default-originate
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# af-group GROUP_2 address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# use af-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# send-community-ebgp
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# send-extended-community-ebgp
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# capability orf prefix both
      

The following example displays sample output from the show bgp af-group command using the configuration keyword. This example shows from where each configuration item was inherited. The default-originate command was configured directly on this address family group (indicated by [ ]). The remove-private-as command was inherited from address family group GROUP_2, which in turn inherited from address family group GROUP_3:

  RP/0/RSP0/CPU0:routershow bgp af-group GROUP_1 configuration 
  
  af-group GROUP_1 address-family ipv4 unicast
    capability orf prefix-list both           [a:GROUP_2]
    default-originate                         []
    maximum-prefix 2500 75 warning-only       []
    route-policy POLICY_1 in                  [a:GROUP_2 a:GROUP_3]
    remove-private-AS                         [a:GROUP_2 a:GROUP_3]
    send-community-ebgp                       [a:GROUP_2]
    send-extended-community-ebgp              [a:GROUP_2]
  
  

The following example displays sample output from the show bgp af-group command using the users keyword:

  RP/0/RSP0/CPU0:routershow bgp af-group GROUP_2 users
  
  IPv4 Unicast: a:GROUP_1
  
  

The following example displays sample output from the show bgp af-group command using the inheritance keyword. This shows that the specified address family group GROUP_1 directly uses the GROUP_2 address family group, which in turn uses the GROUP_3 address family group:

  RP/0/RSP0/CPU0:routershow bgp af-group GROUP_1 inheritance 
  
  IPv4 Unicast: a:GROUP_2 a:GROUP_3
  
show bgp session-group

Use the show bgp session-group command to display session groups:

  • Use the configuration keyword to display the effective configuration for the session group, including any settings that have been inherited from session groups used by this session group.
  • Use the inheritance keyword to display the session groups from which this session group is capable of inheriting configuration.
  • Use the users keyword to display the session groups, neighbor groups, and neighbors that inherit configuration from this session group.

The output from the show bgp session-group command is based on the following session group configuration:

  RP/0/RSP0/CPU0:router(config)# router bgp 113
  RP/0/RSP0/CPU0:router(config-bgp)# session-group GROUP_1
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# use session-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# update-source Loopback 0
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# session-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# use session-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# ebgp-multihop 2
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# session-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# dmz-link-bandwidth
  

The following is sample output from the show bgp session-group command with the configuration keyword in EXEC configuration mode:

  RP/0/RSP0/CPU0:routershow bgp session-group GROUP_1 configuration 
  
  session-group GROUP_1
   ebgp-multihop 2         [s:GROUP_2]
   update-source Loopback0 []
   dmz-link-bandwidth      [s:GROUP_2 s:GROUP_3]
  

The following is sample output from the show bgp session-group command with the inheritance keyword showing that the GROUP_1 session group inherits session parameters from the GROUP_3 and GROUP_2 session groups:

  RP/0/RSP0/CPU0:routershow bgp session-group GROUP_1 inheritance 
  
  Session: s:GROUP_2 s:GROUP_3
  

The following is sample output from the show bgp session-group command with the users keyword showing that both the GROUP_1 and GROUP_2 session groups inherit session parameters from the GROUP_3 session group:

  RP/0/RSP0/CPU0:routershow bgp session-group GROUP_3 users 
  
  Session: s:GROUP_1 s:GROUP_2
  
show bgp neighbor-group

Use the show bgp neighbor-group command to display neighbor groups:

  • Use the configuration keyword to display the effective configuration for the neighbor group, including any settings that have been inherited from neighbor groups used by this neighbor group.
  • Use the inheritance keyword to display the address family groups, session groups, and neighbor groups from which this neighbor group is capable of inheriting configuration.
  • Use the users keyword to display the neighbors and neighbor groups that inherit configuration from this neighbor group.

The examples are based on the following group configuration:

  RP/0/RSP0/CPU0:router(config)# router bgp 140
  RP/0/RSP0/CPU0:router(config-bgp)# af-group GROUP_3 address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# remove-private-as
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# soft-reconfiguration inbound
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# af-group GROUP_2 address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# use af-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# send-community-ebgp
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# send-extended-community-ebgp
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# capability orf prefix both
  RP/0/RSP0/CPU0:router(config-bgp-afgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# session-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# timers 30 90
  RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group GROUP_1
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# remote-as 1982
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# use neighbor-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# exit
  RP/0/RSP0/CPU0:router(config-nbrgrp)# exit
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# use session-group GROUP_3
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:routerconfig-bgp-nbrgrp-af)# use af-group GROUP_2
  RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# weight 100
   

The following is sample output from the show bgp neighbor-group command with the configuration keyword. The configuration setting source is shown to the right of each command. In the output shown previously, the remote autonomous system is configured directly on neighbor group GROUP_1, and the send community setting is inherited from neighbor group GROUP_2, which in turn inherits the setting from address family group GROUP_3:

  RP/0/RSP0/CPU0:routershow bgp neighbor-group GROUP_1 configuration 
  
     neighbor-group GROUP_1
      remote-as 1982                   []
      timers 30 90                     [n:GROUP_2 s:GROUP_3]
      address-family ipv4 unicast      []
       capability orf prefix-list both [n:GROUP_2 a:GROUP_2]
       remove-private-AS               [n:GROUP_2 a:GROUP_2 a:GROUP_3]
       send-community-ebgp             [n:GROUP_2 a:GROUP_2]
       send-extended-community-ebgp    [n:GROUP_2 a:GROUP_2]
       soft-reconfiguration inbound    [n:GROUP_2 a:GROUP_2 a:GROUP_3]
       weight 100                      [n:GROUP_2]
  
  

The following is sample output from the show bgp neighbor-group command with the inheritance keyword. This output shows that the specified neighbor group GROUP_1 inherits session (address family-independent) configuration parameters from neighbor group GROUP_2. Neighbor group GROUP_2 inherits its session parameters from session group GROUP_3. It also shows that the GROUP_1 neighbor group inherits IPv4 unicast configuration parameters from the GROUP_2 neighbor group, which in turn inherits them from the GROUP_2 address family group, which itself inherits them from the GROUP_3 address family group:

  RP/0/RSP0/CPU0:router# show bgp neighbor-group GROUP_1 inheritance 
  
      Session:      n:GROUP-2 s:GROUP_3
      IPv4 Unicast: n:GROUP_2 a:GROUP_2 a:GROUP_3
  
  

The following is sample output from the show bgp neighbor-group command with the users keyword. This output shows that the GROUP_1 neighbor group inherits session (address family-independent) configuration parameters from the GROUP_2 neighbor group. The GROUP_1 neighbor group also inherits IPv4 unicast configuration parameters from the GROUP_2 neighbor group:

  RP/0/RSP0/CPU0:routershow bgp neighbor-group GROUP_2 users 
  
  Session:      n:GROUP_1
  IPv4 Unicast: n:GROUP_1
  

No Default Address Family

BGP does not support the concept of a default address family. An address family must be explicitly configured under the BGP router configuration for the address family to be activated in BGP. Similarly, an address family must be explicitly configured under a neighbor for the BGP session to be activated under that address family. It is not required to have any address family configured under the BGP router configuration level for a neighbor to be configured. However, it is a requirement to have an address family configured at the BGP router configuration level for the address family to be configured under a neighbor.

Routing Policy Enforcement

External BGP (eBGP) neighbors must have an inbound and outbound policy configured. If no policy is configured, no routes are accepted from the neighbor, nor are any routes advertised to it. This added security measure ensures that routes cannot accidentally be accepted or advertised in the case of a configuration omission error.


Note


This enforcement affects only eBGP neighbors (neighbors in a different autonomous system than this router). For internal BGP (iBGP) neighbors (neighbors in the same autonomous system), all routes are accepted or advertised if there is no policy.


In the following example, for an eBGP neighbor, if all routes should be accepted and advertised with no modifications, a simple pass-all policy is configured:

  RP/0/RSP0/CPU0:router(config)# route-policy pass-all
  RP/0/RSP0/CPU0:router(config-rpl)# pass
  RP/0/RSP0/CPU0:router(config-rpl)# end-policy
  RP/0/RSP0/CPU0:router(config)# commit
  

Use the route-policy (BGP) command in the neighbor address-family configuration mode to apply the pass-all policy to a neighbor. The following example shows how to allow all IPv4 unicast routes to be received from neighbor 192.168.40.42 and advertise all IPv4 unicast routes back to it:

  RP/0/RSP0/CPU0:router(config)# router bgp 1
  RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.40.24
  RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 21
  RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy pass-all in
  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy pass-all out
  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# commit
 

Use the show bgp summary command to display eBGP neighbors that do not have both an inbound and outbound policy for every active address family. In the following example, such eBGP neighbors are indicated in the output with an exclamation (!) mark:

  RP/0/RSP0/CPU0:routershow bgp all all summary
  
  Address Family: IPv4 Unicast
  ============================
  
  BGP router identifier 10.0.0.1, local AS number 1
  BGP generic scan interval 60 secs
  BGP main routing table version 41
  BGP scan interval 60 secs
  BGP is operating in STANDALONE mode.
  
  Process         RecvTblVer    bRIB/RIB  SendTblVer
  Speaker                 41          41          41
  
  Neighbor        Spk    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  St/PfxRcd
  10.0.101.1        0     1     919     925       41    0    0 15:15:08       10
  10.0.101.2        0     2       0       0        0    0    0 00:00:00 Idle
  
  
  Address Family: IPv4 Multicast
  ==============================
  
  BGP router identifier 10.0.0.1, local AS number 1
  BGP generic scan interval 60 secs
  BGP main routing table version 1
  BGP scan interval 60 secs
  BGP is operating in STANDALONE mode.
  
  Process         RecvTblVer    bRIB/RIB  SendTblVer
  Speaker                  1           1           1
  
  Some configured eBGP neighbors do not have both inbound and
  outbound policies configured for IPv4 Multicast address family.
  These neighbors will default to sending and/or receiving no
  routes and are marked with ’!’ in the output below. Use the
  ’show bgp neighbor <nbr_address>’ command for details.
  
  Neighbor        Spk    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  St/PfxRcd
  10.0.101.2        0     2       0       0        0    0    0 00:00:00 Idle!
  
  
  Address Family: IPv6 Unicast
  ============================
  
  BGP router identifier 10.0.0.1, local AS number 1
  BGP generic scan interval 60 secs
  BGP main routing table version 2
  BGP scan interval 60 secs
  BGP is operating in STANDALONE mode.
  
  Process         RecvTblVer    bRIB/RIB  SendTblVer
  Speaker                  2           2           2
  
  Neighbor        Spk    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  St/PfxRcd
  2222::2           0     2     920     918        2    0    0 15:15:11        1
  2222::4           0     3       0       0        0    0    0 00:00:00 Idle
  
  
  Address Family: IPv6 Multicast
  ==============================
  
  BGP router identifier 10.0.0.1, local AS number 1
  BGP generic scan interval 60 secs
  BGP main routing table version 1
  BGP scan interval 60 secs
  BGP is operating in STANDALONE mode.
  
  Process         RecvTblVer    bRIB/RIB  SendTblVer
  Speaker                  1           1           1
  
  Some configured eBGP neighbors do not have both inbound and
  outbound policies configured for IPv6 Multicast address family.
  These neighbors will default to sending and/or receiving no
  routes and are marked with ’!’ in the output below. Use the
  ’show bgp neighbor <nbr_address>’ command for details.
  
  Neighbor        Spk    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  St/PfxRcd
  2222::2           0     2     920     918        0    0    0 15:15:11        0
  2222::4           0     3       0       0        0    0    0 00:00:00 Idle!
  

Table Policy

The table policy feature in BGP allows you to configure traffic index values on routes as they are installed in the global routing table. This feature is enabled using the table-policy command and supports the BGP policy accounting feature.

BGP policy accounting uses traffic indices that are set on BGP routes to track various counters. See the Implementing Routing Policy on Cisco ASR 9000 Series Router module in the Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide for details on table policy use. See the Cisco Express Forwarding Commands on Cisco ASR 9000 Series Router module in the Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Command Reference for details on BGP policy accounting.

Table policy also provides the ability to drop routes from the RIB based on match criteria. This feature can be useful in certain applications and should be used with caution as it can easily create a routing ‘black hole’ where BGP advertises routes to neighbors that BGP does not install in its global routing table and forwarding table.

Update Groups

The BGP Update Groups feature contains an algorithm that dynamically calculates and optimizes update groups of neighbors that share outbound policies and can share the update messages. The BGP Update Groups feature separates update group replication from peer group configuration, improving convergence time and flexibility of neighbor configuration.

To use this feature, you must understand the following concepts:

BGP Update Generation and Update Groups

The BGP Update Groups feature separates BGP update generation from neighbor configuration. The BGP Update Groups feature introduces an algorithm that dynamically calculates BGP update group membership based on outbound routing policies. This feature does not require any configuration by the network operator. Update group-based message generation occurs automatically and independently.

BGP Update Group

When a change to the configuration occurs, the router automatically recalculates update group memberships and applies the changes.

For the best optimization of BGP update group generation, we recommend that the network operator keeps outbound routing policy the same for neighbors that have similar outbound policies. This feature contains commands for monitoring BGP update groups. For more information about the commands, see Monitoring BGP Update Groups.

BGP Cost Community

The BGP cost community is a nontransitive extended community attribute that is passed to internal BGP (iBGP) and confederation peers but not to external BGP (eBGP) peers. The cost community feature allows you to customize the local route preference and influence the best-path selection process by assigning cost values to specific routes. The extended community format defines generic points of insertion (POI) that influence the best-path decision at different points in the best-path algorithm.

The cost community attribute is applied to internal routes by configuring the set extcommunity cost command in a route policy. See the Routing Policy Language Commands on Cisco ASR 9000 Series Router module of Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference for information on the set extcommunity cost command. The cost community set clause is configured with a cost community ID number (0–255) and cost community number (0–4294967295). The cost community number determines the preference for the path. The path with the lowest cost community number is preferred. Paths that are not specifically configured with the cost community number are assigned a default cost community number of 2147483647 (the midpoint between 0 and 4294967295) and evaluated by the best-path selection process accordingly. When two paths have been configured with the same cost community number, the path selection process prefers the path with the lowest cost community ID. The cost-extended community attribute is propagated to iBGP peers when extended community exchange is enabled.

The following commands include the route-policy keyword, which you can use to apply a route policy that is configured with the cost community set clause:

  • aggregate-address
  • redistribute
  • network

How BGP Cost Community Influences the Best Path Selection Process

The cost community attribute influences the BGP best-path selection process at the point of insertion (POI). By default, the POI follows the Interior Gateway Protocol (IGP) metric comparison. When BGP receives multiple paths to the same destination, it uses the best-path selection process to determine which path is the best path. BGP automatically makes the decision and installs the best path in the routing table. The POI allows you to assign a preference to a specific path when multiple equal cost paths are available. If the POI is not valid for local best-path selection, the cost community attribute is silently ignored.

Cost communities are sorted first by POI then by community ID. Multiple paths can be configured with the cost community attribute for the same POI. The path with the lowest cost community ID is considered first. In other words, all cost community paths for a specific POI are considered, starting with the one with the lowest cost community. Paths that do not contain the cost community cost (for the POI and community ID being evaluated) are assigned the default community cost value (2147483647). If the cost community values are equal, then cost community comparison proceeds to the next lowest community ID for this POI.

To select the path with the lower cost community, simultaneously walk through the cost communities of both paths. This is done by maintaining two pointers to the cost community chain, one for each path, and advancing both pointers to the next applicable cost community at each step of the walk for the given POI, in order of community ID, and stop when a best path is chosen or the comparison is a tie. At each step of the walk, the following checks are done:

  If neither pointer refers to a cost community,
       Declare a tie;
  
    Elseif a cost community is found for one path but not for the other,
       Choose the path with cost community as best path;
    Elseif the Community ID from one path is less than the other,
       Choose the path with the lesser Community ID as best path;
    Elseif the Cost from one path is less than the other,
       Choose the path with the lesser Cost as best path;
    Else Continue.
  

Note


Paths that are not configured with the cost community attribute are considered by the best-path selection process to have the default cost value (half of the maximum value [4294967295] or 2147483647).


Applying the cost community attribute at the POI allows you to assign a value to a path originated or learned by a peer in any part of the local autonomous system or confederation. The cost community can be used as a “tie breaker” during the best-path selection process. Multiple instances of the cost community can be configured for separate equal cost paths within the same autonomous system or confederation. For example, a lower cost community value can be applied to a specific exit path in a network with multiple equal cost exit points, and the specific exit path is preferred by the BGP best-path selection process. See the scenario described inInfluencing Route Preference in a Multiexit IGP Network.


Note


The cost community comparison in BGP is enabled by default. Use the bgp bestpath cost-community ignore command to disable the comparison.


SeeBGP Best Path Algorithm for information on the BGP best-path selection process.

Cost Community Support for Aggregate Routes and Multipaths

The BGP cost community feature supports aggregate routes and multipaths. The cost community attribute can be applied to either type of route. The cost community attribute is passed to the aggregate or multipath route from component routes that carry the cost community attribute. Only unique IDs are passed, and only the highest cost of any individual component route is applied to the aggregate for each ID. If multiple component routes contain the same ID, the highest configured cost is applied to the route. For example, the following two component routes are configured with the cost community attribute using an inbound route policy:

  • 10.0.0.1
    • POI=IGP
    • cost community ID=1
    • cost number=100
  • 192.168.0.1
    • POI=IGP
    • cost community ID=1
    • cost number=200
    If these component routes are aggregated or configured as a multipath, the cost value 200 is advertised, because it has the highest cost. If one or more component routes do not carry the cost community attribute or the component routes are configured with different IDs, then the default value (2147483647) is advertised for the aggregate or multipath route. For example, the following three component routes are configured with the cost community attribute using an inbound route policy. However, the component routes are configured with two different IDs.
  • 10.0.0.1
    • POI=IGP
    • cost community ID=1
    • cost number=100
  • 172.16.0.1
    • POI=IGP
    • cost community ID=2
    • cost number=100
  • 192.168.0.1
    • POI=IGP
    • cost community ID=1
    • cost number=200
    The single advertised path includes the aggregate cost communities as follows: {POI=IGP, ID=1, Cost=2147483647} {POI-IGP, ID=2, Cost=2147483647}

Influencing Route Preference in a Multiexit IGP Network

This figure shows an IGP network with two autonomous system boundary routers (ASBRs) on the edge. Each ASBR has an equal cost path to network 10.8/16.

Figure 1. Multiexit Point IGP Network

Both paths are considered to be equal by BGP. If multipath loadsharing is configured, both paths to the routing table are installed and are used to balance the load of traffic. If multipath load balancing is not configured, the BGP selects the path that was learned first as the best path and installs this path to the routing table. This behavior may not be desirable under some conditions. For example, the path is learned from ISP1 PE2 first, but the link between ISP1 PE2 and ASBR1 is a low-speed link.

The configuration of the cost community attribute can be used to influence the BGP best-path selection process by applying a lower-cost community value to the path learned by ASBR2. For example, the following configuration is applied to ASBR2:

RP/0/RSP0/CPU0:router(config)# route-policy ISP2_PE1
RP/0/RSP0/CPU0:router(config-rpl)# set extcommunity cost (1:1)

The preceding route policy applies a cost community number of 1 to the 10.8.0.0 route. By default, the path learned from ASBR1 is assigned a cost community number of 2147483647. Because the path learned from ASBR2 has a lower-cost community number, the path is preferred.

BGP Cost Community Support for EIGRP MPLS VPN PE-CE with Back-door Links

Back-door links in an EIGRP MPLS VPN topology is preferred by BGP if the back-door link is learned first. (A back-door link, or route, is a connection that is configured outside of the VPN between a remote and main site; for example, a WAN leased line that connects a remote site to the corporate network.)

The “prebest path” point of insertion (POI) in the BGP cost community feature supports mixed EIGRP VPN network topologies that contain VPN and back-door links. This POI is applied automatically to EIGRP routes that are redistributed into BGP. The “prebest path” POI carries the EIGRP route type and metric. This POI influences the best-path calculation process by influencing BGP to consider the POI before any other comparison step. No configuration is required. This feature is enabled automatically for EIGRP VPN sites when Cisco IOS XR software is installed on a PE, CE, or back-door router.

For information about configuring EIGRP MPLS VPNs, see the Cisco ASR 9000 Series Aggregation Services Router MPLS Configuration Guide.

Figure 2. Network Showing How Cost Community Can be Used to Support Backdoor Links.

This figure shows how cost community can be used to support backdoor links in a network.



The following sequence of events happens in PE1:

  1. PE1 learns IPv4 prefix 10.1.1.0/24 from CE1 through EIGRP running a virtual routing and forwarding (VRF) instance. EIGRP selects and installs the best path in the RIB. It also encodes the cost-extended community and adds the information to the RIB.
  2. The route is redistributed into BGP (assuming that IGP-to-BGP redistribution is configured). BGP also receives the cost-extended community from the route through the redistribution process.
  3. After BGP has determined the best path for the newly redistributed prefix, the path is advertised to PE peers (PE2).
  4. PE2 receives the BGP VPNv4 prefix route_distinguisher:10.1.1.0/24 along with the cost community. It is likely that CE2 advertises the same prefix (because of the back-door link between CE1 and CE2) to PE2 through EIGRP. PE2 BGP would have already learned the CE route through the redistribution process along with the cost community value
  5. PE2 has two paths within BGP: one with cost community cost1 through multipath BGP (PE1) and another with cost community cost2 through the EIGRP neighbor (CE2).
  6. PE2 runs the enhanced BGP best-path calculation.
  7. PE2 installs the best path in the RIB passing the appropriate cost community value.
  8. PE2 RIB has two paths for 10.1.1.0/24: one with cost community cost2 added by EIGRP and another with the cost community cost1 added by BGP. Because both the route paths have cost community, RIB compares the costs first. The BGP path has the lower cost community, so it is selected and downloaded to the RIB.
  9. PE2 RIB redistributes the BGP path into EIGRP with VRF. EIGRP runs a diffusing update algorithm (DUAL) because there are two paths, and selects the BGP-redistributed path.
  10. PE2 EIGRP advertises the path to CE2 making the path the next hop for the prefix to send the traffic over the MPLS network.

Adding Routes to the Routing Information Base

If a nonsourced path becomes the best path after the best-path calculation, BGP adds the route to the Routing Information Base (RIB) and passes the cost communities along with the other IGP extended communities.

When a route with paths is added to the RIB by a protocol, RIB checks the current best paths for the route and the added paths for cost extended communities. If cost-extended communities are found, the RIB compares the set of cost communities. If the comparison does not result in a tie, the appropriate best path is chosen. If the comparison results in a tie, the RIB proceeds with the remaining steps of the best-path algorithm. If a cost community is not present in either the current best paths or added paths, then the RIB continues with the remaining steps of the best-path algorithm. See BGP Best Path Algorithm for information on the BGP best-path algorithm.

BGP Best Path Algorithm

BGP routers typically receive multiple paths to the same destination. The BGP best-path algorithm determines the best path to install in the IP routing table and to use for forwarding traffic. This section describes the Cisco IOS XR software implementation of BGP best-path algorithm, as specified in Section 9.1 of the Internet Engineering Task Force (IETF) Network Working Group draft-ietf-idr-bgp4-24.txt document.

The BGP best-path algorithm implementation is in three parts:

  • Part 1—Compares two paths to determine which is better.
  • Part 2—Iterates over all paths and determines which order to compare the paths to select the overall best path.
  • Part 3—Determines whether the old and new best paths differ enough so that the new best path should be used.

Note


The order of comparison determined by Part 2 is important because the comparison operation is not transitive; that is, if three paths, A, B, and C exist, such that when A and B are compared, A is better, and when B and C are compared, B is better, it is not necessarily the case that when A and C are compared, A is better. This nontransitivity arises because the multi exit discriminator (MED) is compared only among paths from the same neighboring autonomous system (AS) and not among all paths.


Comparing Pairs of Paths

Perform the following steps to compare two paths and determine the better path:

  1. If either path is invalid (for example, a path has the maximum possible MED value or it has an unreachable next hop), then the other path is chosen (provided that the path is valid).
  2. If the paths have unequal pre-bestpath cost communities, the path with the lower pre-bestpath cost community is selected as the best path.

    Note


    See BGP Cost Community for details on how cost communities are compared.


  3. If the paths have unequal weights, the path with the highest weight is chosen.

    Note


    The weight is entirely local to the router, and can be set with the weight command or using a routing policy.


  4. If the paths have unequal local preferences, the path with the higher local preference is chosen.

    Note


    If a local preference attribute was received with the path or was set by a routing policy, then that value is used in this comparison. Otherwise, the default local preference value of 100 is used. The default value can be changed using the bgp default local-preference command.


  5. If one of the paths is a redistributed path, which results from a redistribute or network command, then it is chosen. Otherwise, if one of the paths is a locally generated aggregate, which results from an aggregate-address command, it is chosen.

    Note


    Step 1 through Step 4 implement the “Path Selection with BGP”of RFC 1268.


  6. If the paths have unequal AS path lengths, the path with the shorter AS path is chosen. This step is skipped if bgp bestpath as-path ignore command is configured.

    Note


    When calculating the length of the AS path, confederation segments are ignored, and AS sets count as 1.



    Note


    eiBGP specifies internal and external BGP multipath peers. eiBGP allows simultaneous use of internal and external paths.


  7. If the paths have different origins, the path with the lower origin is selected. Interior Gateway Protocol (IGP) is considered lower than EGP, which is considered lower than INCOMPLETE.
  8. If appropriate, the MED of the paths is compared. If they are unequal, the path with the lower MED is chosen. A number of configuration options exist that affect whether or not this step is performed. In general, the MED is compared if both paths were received from neighbors in the same AS; otherwise the MED comparison is skipped. However, this behavior is modified by certain configuration options, and there are also some corner cases to consider. If the bgp bestpath med always command is configured, then the MED comparison is always performed, regardless of neighbor AS in the paths. Otherwise, MED comparison depends on the AS paths of the two paths being compared, as follows:
    • If a path has no AS path or the AS path starts with an AS_SET, then the path is considered to be internal, and the MED is compared with other internal paths.
    • If the AS path starts with an AS_SEQUENCE, then the neighbor AS is the first AS number in the sequence, and the MED is compared with other paths that have the same neighbor AS.
    • If the AS path contains only confederation segments or starts with confederation segments followed by an AS_SET, then the MED is not compared with any other path unless the bgp bestpath med confed command is configured. In that case, the path is considered internal and the MED is compared with other internal paths.
    • If the AS path starts with confederation segments followed by an AS_SEQUENCE, then the neighbor AS is the first AS number in the AS_SEQUENCE, and the MED is compared with other paths that have the same neighbor AS.

    Note


    If no MED attribute was received with the path, then the MED is considered to be 0 unless the bgp bestpath med missing-as-worst command is configured. In that case, if no MED attribute was received, the MED is considered to be the highest possible value.


  9. If one path is received from an external peer and the other is received from an internal (or confederation) peer, the path from the external peer is chosen.
  10. If the paths have different IGP metrics to their next hops, the path with the lower IGP metric is chosen.
  11. If the paths have unequal IP cost communities, the path with the lower IP cost community is selected as the best path.

    Note


    See the BGP Cost Community for details on how cost communities are compared.


  12. If all path parameters in Step 1 through Step 10 are the same, then the router IDs are compared. If the path was received with an originator attribute, then that is used as the router ID to compare; otherwise, the router ID of the neighbor from which the path was received is used. If the paths have different router IDs, the path with the lower router ID is chosen.

    Note


    Where the originator is used as the router ID, it is possible to have two paths with the same router ID. It is also possible to have two BGP sessions with the same peer router, and therefore receive two paths with the same router ID.


  13. If the paths have different cluster lengths, the path with the shorter cluster length is selected. If a path was not received with a cluster list attribute, it is considered to have a cluster length of 0.
  14. Finally, the path received from the neighbor with the lower IP address is chosen. Locally generated paths (for example, redistributed paths) are considered to have a neighbor IP address of 0.

Order of Comparisons

The second part of the BGP best-path algorithm implementation determines the order in which the paths should be compared. The order of comparison is determined as follows:

  1. The paths are partitioned into groups such that within each group the MED can be compared among all paths. The same rules as in Comparing Pairs of Paths are used to determine whether MED can be compared between any two paths. Normally, this comparison results in one group for each neighbor AS. If the bgp bestpath med always command is configured, then there is just one group containing all the paths.
  2. The best path in each group is determined. Determining the best path is achieved by iterating through all paths in the group and keeping track of the best one seen so far. Each path is compared with the best-so-far, and if it is better, it becomes the new best-so-far and is compared with the next path in the group.
  3. A set of paths is formed containing the best path selected from each group in Step 2. The overall best path is selected from this set of paths, by iterating through them as in Step 2.

Best Path Change Suppression

The third part of the implementation is to determine whether the best-path change can be suppressed or not—whether the new best path should be used, or continue using the existing best path. The existing best path can continue to be used if the new one is identical to the point at which the best-path selection algorithm becomes arbitrary (if the router-id is the same). Continuing to use the existing best path can avoid churn in the network.


Note


This suppression behavior does not comply with the IETF Networking Working Group draft-ietf-idr-bgp4-24.txt document, but is specified in the IETF Networking Working Group draft-ietf-idr-avoid-transition-00.txt document.


The suppression behavior can be turned off by configuring the bgp bestpath compare-routerid command. If this command is configured, the new best path is always preferred to the existing one.

Otherwise, the following steps are used to determine whether the best-path change can be suppressed:

  1. If the existing best path is no longer valid, the change cannot be suppressed.
  2. If either the existing or new best paths were received from internal (or confederation) peers or were locally generated (for example, by redistribution), then the change cannot be suppressed. That is, suppression is possible only if both paths were received from external peers.
  3. If the paths were received from the same peer (the paths would have the same router-id), the change cannot be suppressed. The router ID is calculated using rules in Comparing Pairs of Paths.
  4. If the paths have different weights, local preferences, origins, or IGP metrics to their next hops, then the change cannot be suppressed. Note that all these values are calculated using the rules in Comparing Pairs of Paths.
  5. If the paths have different-length AS paths and the bgp bestpath as-path ignore command is not configured, then the change cannot be suppressed. Again, the AS path length is calculated using the rules in Comparing Pairs of Paths.
  6. If the MED of the paths can be compared and the MEDs are different, then the change cannot be suppressed. The decision as to whether the MEDs can be compared is exactly the same as the rules in Comparing Pairs of Paths, as is the calculation of the MED value.
  7. If all path parameters in Step 1 through Step 6 do not apply, the change can be suppressed.

Administrative Distance

An administrative distance is a rating of the trustworthiness of a routing information source. In general, the higher the value, the lower the trust rating. For information on specifying the administrative distance for BGP, see the BGP Commands module of the Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference

Normally, a route can be learned through more than one protocol. Administrative distance is used to discriminate between routes learned from more than one protocol. The route with the lowest administrative distance is installed in the IP routing table. By default, BGP uses the administrative distances shown in Table 1.

Table 1 BGP Default Administrative Distances

Distance

Default Value

Function

External

20

Applied to routes learned from eBGP.

Internal

200

Applied to routes learned from iBGP.

Local

200

Applied to routes originated by the router.


Note


Distance does not influence the BGP path selection algorithm, but it does influence whether BGP-learned routes are installed in the IP routing table.


In most cases, when a route is learned through eBGP, it is installed in the IP routing table because of its distance (20). Sometimes, however, two ASs have an IGP-learned back-door route and an eBGP-learned route. Their policy might be to use the IGP-learned path as the preferred path and to use the eBGP-learned path when the IGP path is down. See Figure 1.

Figure 3. Back Door Example

In Figure 1, Routers A and C and Routers B and C are running eBGP. Routers A and B are running an IGP (such as Routing Information Protocol [RIP], Interior Gateway Routing Protocol [IGRP], Enhanced IGRP, or Open Shortest Path First [OSPF]). The default distances for RIP, IGRP, Enhanced IGRP, and OSPF are 120, 100, 90, and 110, respectively. All these distances are higher than the default distance of eBGP, which is 20. Usually, the route with the lowest distance is preferred.

Router A receives updates about 160.10.0.0 from two routing protocols: eBGP and IGP. Because the default distance for eBGP is lower than the default distance of the IGP, Router A chooses the eBGP-learned route from Router C. If you want Router A to learn about 160.10.0.0 from Router B (IGP), establish a BGP back door. See .

In the following example, a network back-door is configured:

RP/0/RSP0/CPU0:router(config)# router bgp 100
RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router(config-bgp-af)# network 160.10.0.0/16 backdoor

Router A treats the eBGP-learned route as local and installs it in the IP routing table with a distance of 200. The network is also learned through Enhanced IGRP (with a distance of 90), so the Enhanced IGRP route is successfully installed in the IP routing table and is used to forward traffic. If the Enhanced IGRP-learned route goes down, the eBGP-learned route is installed in the IP routing table and is used to forward traffic.

Although BGP treats network 160.10.0.0 as a local entry, it does not advertise network 160.10.0.0 as it normally would advertise a local entry.

Multiprotocol BGP

Multiprotocol BGP is an enhanced BGP that carries routing information for multiple network layer protocols and IP multicast routes. BGP carries two sets of routes, one set for unicast routing and one set for multicast routing. The routes associated with multicast routing are used by the Protocol Independent Multicast (PIM) feature to build data distribution trees.

Multiprotocol BGP is useful when you want a link dedicated to multicast traffic, perhaps to limit which resources are used for which traffic. Multiprotocol BGP allows you to have a unicast routing topology different from a multicast routing topology providing more control over your network and resources.

In BGP, the only way to perform interdomain multicast routing was to use the BGP infrastructure that was in place for unicast routing. Perhaps you want all multicast traffic exchanged at one network access point (NAP). If those routers were not multicast capable, or there were differing policies for which you wanted multicast traffic to flow, multicast routing could not be supported without multiprotocol BGP.


Note


It is possible to configure BGP peers that exchange both unicast and multicast network layer reachability information (NLRI), but you cannot connect multiprotocol BGP clouds with a BGP cloud. That is, you cannot redistribute multiprotocol BGP routes into BGP.


Figure 1 illustrates simple unicast and multicast topologies that are incongruent, and therefore are not possible without multiprotocol BGP.

Autonomous systems 100, 200, and 300 are each connected to two NAPs that are FDDI rings. One is used for unicast peering (and therefore the exchange of unicast traffic). The Multicast Friendly Interconnect (MFI) ring is used for multicast peering (and therefore the exchange of multicast traffic). Each router is unicast and multicast capable.

Figure 4. Noncongruent Unicast and Multicast Routes

Figure 2 is a topology of unicast-only routers and multicast-only routers. The two routers on the left are unicast-only routers (that is, they do not support or are not configured to perform multicast routing). The two routers on the right are multicast-only routers. Routers A and B support both unicast and multicast routing. The unicast-only and multicast-only routers are connected to a single NAP.

In Figure 2, only unicast traffic can travel from Router A to the unicast routers to Router B and back. Multicast traffic could not flow on that path, so another routing table is required. Multicast traffic uses the path from Router A to the multicast routers to Router B and back.

Figure 2 illustrates a multiprotocol BGP environment with a separate unicast route and multicast route from Router A to Router B. Multiprotocol BGP allows these routes to be incongruent. Both of the autonomous systems must be configured for internal multiprotocol BGP (IMBGP) in the figure.

A multicast routing protocol, such as PIM, uses the multicast BGP database to perform Reverse Path Forwarding (RPF) lookups for multicast-capable sources. Thus, packets can be sent and accepted on the multicast topology but not on the unicast topology.

Figure 5. Multicast BGP Environment

Route Dampening

Route dampening is a BGP feature that minimizes the propagation of flapping routes across an internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable, then available, then unavailable, and so on.

For example, consider a network with three BGP autonomous systems: autonomous system 1, autonomous system 2, and autonomous system 3. Suppose the route to network A in autonomous system 1 flaps (it becomes unavailable). Under circumstances without route dampening, the eBGP neighbor of autonomous system 1 to autonomous system 2 sends a withdraw message to autonomous system 2. The border router in autonomous system 2, in turn, propagates the withdrawal message to autonomous system 3. When the route to network A reappears, autonomous system 1 sends an advertisement message to autonomous system 2, which sends it to autonomous system 3. If the route to network A repeatedly becomes unavailable, then available, many withdrawal and advertisement messages are sent. Route flapping is a problem in an internetwork connected to the Internet, because a route flap in the Internet backbone usually involves many routes.

Minimizing Flapping

The route dampening feature minimizes the flapping problem as follows. Suppose again that the route to network A flaps. The router in autonomous system 2 (in which route dampening is enabled) assigns network A a penalty of 1000 and moves it to history state. The router in autonomous system 2 continues to advertise the status of the route to neighbors. The penalties are cumulative. When the route flaps so often that the penalty exceeds a configurable suppression limit, the router stops advertising the route to network A, regardless of how many times it flaps. Thus, the route is dampened.

The penalty placed on network A is decayed until the reuse limit is reached, upon which the route is once again advertised. At half of the reuse limit, the dampening information for the route to network A is removed.


Note


No penalty is applied to a BGP peer reset when route dampening is enabled, even though the reset withdraws the route.


BGP Routing Domain Confederation

One way to reduce the iBGP mesh is to divide an autonomous system into multiple subautonomous systems and group them into a single confederation. To the outside world, the confederation looks like a single autonomous system. Each autonomous system is fully meshed within itself and has a few connections to other autonomous systems in the same confederation. Although the peers in different autonomous systems have eBGP sessions, they exchange routing information as if they were iBGP peers. Specifically, the next hop, MED, and local preference information is preserved. This feature allows you to retain a single IGP for all of the autonomous systems.

BGP Route Reflectors

BGP requires that all iBGP speakers be fully meshed. However, this requirement does not scale well when there are many iBGP speakers. Instead of configuring a confederation, you can reduce the iBGP mesh by using a route reflector configuration.

Figure 1 illustrates a simple iBGP configuration with three iBGP speakers (routers A, B, and C). Without route reflectors, when Router A receives a route from an external neighbor, it must advertise it to both routers B and C. Routers B and C do not readvertise the iBGP learned route to other iBGP speakers because the routers do not pass on routes learned from internal neighbors to other internal neighbors, thus preventing a routing information loop.

Figure 6. Three Fully Meshed iBGP Speakers

With route reflectors, all iBGP speakers need not be fully meshed because there is a method to pass learned routes to neighbors. In this model, an iBGP peer is configured to be a route reflector responsible for passing iBGP learned routes to a set of iBGP neighbors. In Figure 2 , Router B is configured as a route reflector. When the route reflector receives routes advertised from Router A, it advertises them to Router C, and vice versa. This scheme eliminates the need for the iBGP session between routers A and C.

Figure 7. Simple BGP Model with a Route Reflector

The internal peers of the route reflector are divided into two groups: client peers and all other routers in the autonomous system (nonclient peers). A route reflector reflects routes between these two groups. The route reflector and its client peers form a cluster. The nonclient peers must be fully meshed with each other, but the client peers need not be fully meshed. The clients in the cluster do not communicate with iBGP speakers outside their cluster.

Figure 8. More Complex BGP Route Reflector Model

Figure 3 illustrates a more complex route reflector scheme. Router A is the route reflector in a cluster with routers B, C, and D. Routers E, F, and G are fully meshed, nonclient routers.

When the route reflector receives an advertised route, depending on the neighbor, it takes the following actions:

  • A route from an external BGP speaker is advertised to all clients and nonclient peers.
  • A route from a nonclient peer is advertised to all clients.
  • A route from a client is advertised to all clients and nonclient peers. Hence, the clients need not be fully meshed.

Along with route reflector-aware BGP speakers, it is possible to have BGP speakers that do not understand the concept of route reflectors. They can be members of either client or nonclient groups, allowing an easy and gradual migration from the old BGP model to the route reflector model. Initially, you could create a single cluster with a route reflector and a few clients. All other iBGP speakers could be nonclient peers to the route reflector and then more clusters could be created gradually.

An autonomous system can have multiple route reflectors. A route reflector treats other route reflectors just like other iBGP speakers. A route reflector can be configured to have other route reflectors in a client group or nonclient group. In a simple configuration, the backbone could be divided into many clusters. Each route reflector would be configured with other route reflectors as nonclient peers (thus, all route reflectors are fully meshed). The clients are configured to maintain iBGP sessions with only the route reflector in their cluster.

Usually, a cluster of clients has a single route reflector. In that case, the cluster is identified by the router ID of the route reflector. To increase redundancy and avoid a single point of failure, a cluster might have more than one route reflector. In this case, all route reflectors in the cluster must be configured with the cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster. All route reflectors serving a cluster should be fully meshed and all of them should have identical sets of client and nonclient peers.

By default, the clients of a route reflector are not required to be fully meshed and the routes from a client are reflected to other clients. However, if the clients are fully meshed, the route reflector need not reflect routes to clients.

As the iBGP learned routes are reflected, routing information may loop. The route reflector model has the following mechanisms to avoid routing loops:

  • Originator ID is an optional, nontransitive BGP attribute. It is a 4-byte attributed created by a route reflector. The attribute carries the router ID of the originator of the route in the local autonomous system. Therefore, if a misconfiguration causes routing information to come back to the originator, the information is ignored.
  • Cluster-list is an optional, nontransitive BGP attribute. It is a sequence of cluster IDs that the route has passed. When a route reflector reflects a route from its clients to nonclient peers, and vice versa, it appends the local cluster ID to the cluster-list. If the cluster-list is empty, a new cluster-list is created. Using this attribute, a route reflector can identify if routing information is looped back to the same cluster due to misconfiguration. If the local cluster ID is found in the cluster-list, the advertisement is ignored.

Default Address Family for show Commands

Most of the show commands provide address family (AFI) and subaddress family (SAFI) arguments (see RFC 1700 and RFC 2858 for information on AFI and SAFI). The Cisco IOS XR software parser provides the ability to set the afi and safi so that it is not necessary to specify them while running a show command. The parser commands are:

  • set default-afi { ipv4 | ipv6 | all }
  • set default-safi { unicast | multicast | all }

The parser automatically sets the default afi value to ipv4 and default safi value to unicast . It is necessary to use only the parser commands to change the default afi value from ipv4 or default safi value from unicast . Any afi or safi keyword specified in a show command overrides the values set using the parser commands. Use the following show default-afi-safi-vrf command to check the currently set value of the afi and safi.

MPLS VPN Carrier Supporting Carrier

Carrier supporting carrier (CSC) is a term used to describe a situation in which one service provider allows another service provider to use a segment of its backbone network. The service provider that provides the segment of the backbone network to the other provider is called the backbone carrier. The service provider that uses the segment of the backbone network is called the customer carrier.

A backbone carrier offers Border Gateway Protocol and Multiprotocol Label Switching (BGP/MPLS) VPN services. The customer carrier can be either:

  • An Internet service provider (ISP) (By definition, an ISP does not provide VPN service.)
  • A BGP/MPLS VPN service provider

You can configure a CSC network to enable BGP to transport routes and MPLS labels between the backbone carrier provider edge (PE) routers and the customer carrier customer edge (CE) routers using multiple paths. The benefits of using BGP to distribute IPv4 routes and MPLS label routes are:

  • BGP takes the place of an Interior Gateway Protocol (IGP) and Label Distribution Protocol (LDP) in a VPN routing and forwarding (VRF) table. You can use BGP to distribute routes and MPLS labels. Using a single protocol instead of two simplifies the configuration and troubleshooting.
  • BGP is the preferred routing protocol for connecting two ISPs, mainly because of its routing policies and ability to scale. ISPs commonly use BGP between two providers. This feature enables those ISPs to use BGP.

For detailed information on configuring MPLS VPN CSC with BGP, see the Implementing MPLS Layer 3 VPNs on Cisco ASR 9000 Series Router module of the Cisco ASR 9000 Series Aggregation Services Router MPLS Configuration Guide.

BGP Keychains

BGP keychains enable keychain authentication between two BGP peers. The BGP endpoints must both comply with draft-bonica-tcp-auth-05.txt and a keychain on one endpoint and a password on the other endpoint does not work.

See the Cisco ASR 9000 Series Aggregation Services Router System Security Configuration Guide for information on keychain management.

BGP is able to use the keychain to implement hitless key rollover for authentication. Key rollover specification is time based, and in the event of clock skew between the peers, the rollover process is impacted. The configurable tolerance specification allows for the accept window to be extended (before and after) by that margin. This accept window facilitates a hitless key rollover for applications (for example, routing and management protocols).

The key rollover does not impact the BGP session, unless there is a keychain configuration mismatch at the endpoints resulting in no common keys for the session traffic (send or accept).

BGP Nonstop Routing

The Border Gateway Protocol (BGP) Nonstop Routing (NSR) with Stateful Switchover (SSO) feature enables all bgp peerings to maintain the BGP state and ensure continuous packet forwarding during events that could interrupt service. Under NSR, events that might potentially interrupt service are not visible to peer routers. Protocol sessions are not interrupted and routing states are maintained across process restarts and switchovers.

BGP NSR provides nonstop routing during the following events:

  • Route processor switchover
  • Process crash or process failure of BGP or TCP

    Note


    In case of process crash or process failure, NSR will be maintained only if nsr process-failures switchover command is configured. In the event of process failures of active instances, the nsr process-failures switchover configures failover as a recovery action and switches over to a standby route processor (RP) or a standby distributed route processor (DRP) thereby maintaining NSR.

    The nsr process-failures switchover command maintains both the NSR and BGP sessions in the event of a BGP or TCP process crash. Without this configuration, BGP neighbor sessions flap in case of a BGP or TCP process crash. This configuration does not help if the BGP or TCP process is restarted in which case the BGP neighbors are expected to flap.


During route processor switchover and In-Service System Upgrade (ISSU), NSR is achieved by stateful switchover (SSO) of both TCP and BGP.

NSR does not force any software upgrades on other routers in the network, and peer routers are not required to support NSR.

When a route processor switchover occurs due to a fault, the TCP connections and the BGP sessions are migrated transparently to the standby route processor, and the standby route processor becomes active. The existing protocol state is maintained on the standby route processor when it becomes active, and the protocol state does not need to be refreshed by peers.

Events such as soft reconfiguration and policy modifications can trigger the BGP internal state to change. To ensure state consistency between active and standby BGP processes during such events, the concept of post-it is introduced that act as synchronization points.

BGP NSR provides the following features:

  • NSR-related alarms and notifications
  • Configured and operational NSR states are tracked separately
  • NSR statistics collection
  • NSR statistics display using show commands
  • XML schema support
  • Auditing mechanisms to verify state synchronization between active and standby instances
  • CLI commands to enable and disable NSR
  • Support for 5000 NSR sessions

BGP Prefix Independent Convergence Unipath Primary/Backup

The Border Gateway Protocol Prefix Independent Convergence Unipath (BGP PIC Unipath) primary/backup feature provides the capability to install a backup path into the forwarding table. Installing the backup path provides prefix independent convergence in the event of a primary PE–CE link failure.

The primary/backup path provides a mechanism for BGP to determine a backup best path. The backup best path acts as a backup to the overall best path, which is the primary best path. BGP programs both the paths into the Forwarding Information Base (FIB).

The procedure to determine the backup best path is as follows:

  1. Determine the best path from the entire set of paths available for a prefix.
  2. Eliminate the current best path.
  3. Eliminate all the paths that have the same next hop as that of the current best path.
  4. Rerun the best path algorithm on the remaining set of paths to determine the backup best path.

The PE-CE local convergence is in the order of four to five seconds for 10000 prefixes. Installing a backup path on the linecards, so that the Forwarding Information Base (FIB) can immediately switch to an alternate path, in the event of a primary PE-CE link failure reduces the convergence time.

In the case of primary PE-CE link failure, the FIB starts forwarding the received traffic towards the backup PE. FIB will continue forwarding the received traffic towards the backup PE for the duration of the network convergence. Since the approach of using a backup path is independent to the prefixes, Prefix Independent Convergence Unipath functionality provides a prefix independent sub second convergence.

The additional-paths selection command installs the backup path in the Forwarding Information Base (FIB) to enable primary backup path.

BGP Local Label Retention

When a primary PE-CE link fails, BGP withdraws the route corresponding to the primary path along with its local label and programs the backup path in the Routing Information Base (RIB) and the Forwarding Information Base (FIB), by default.

However, until all the internal peers of the primary PE reconverge to use the backup path as the new bestpath, the traffic continues to be forwarded to the primary PE with the local label that was allocated for the primary path. Hence the previously allocated local label for the primary path must be retained on the primary PE for some configurable time after the reconvergence. BGP Local Label Retention feature enables the retention of the local label for a specified period. If no time is specified, the local lable is retained for a default value of five minutes.

The retain local-label command enables the retention of the local label until the network is converged.

Command Line Interface (CLI) Consistency for BGP Commands

From Cisco IOS XR Release 3.9.0 onwards, the Border Gateway Protocol (BGP) commands use disable keyword to disable a feature. The keyword inheritance-disable disables the inheritance of the feature properties from the parent level.

BGP Additional Paths

The Border Gateway Protocol (BGP) Additional Paths feature modifies the BGP protocol machinery for a BGP speaker to be able to send multiple paths for a prefix. This gives 'path diversity' in the network. The add path enables BGP prefix independent convergence (PIC) at the edge routers.

BGP add path enables add path advertisement in an iBGP network and advertises the following types of paths for a prefix:

  • Backup paths—to enable fast convergence and connectivity restoration.
  • Group-best paths—to resolve route oscillation.
  • All paths—to emulate an iBGP full-mesh.

    Note


    Add path is not be supported with MDT, tunnel, and L2VPN address families and eBGP peerings.

iBGP Multipath Load Sharing

When a Border Gateway Protocol (BGP) speaking router that has no local policy configured, receives multiple network layer reachability information (NLRI) from the internal BGP (iBGP) for the same destination, the router will choose one iBGP path as the best path. The best path is then installed in the IP routing table of the router.

The iBGP Multipath Load Sharing feature enables the BGP speaking router to select multiple iBGP paths as the best paths to a destination. The best paths or multipaths are then installed in the IP routing table of the router.

When there are multiple border BGP routers having reachability information heard over eBGP, if no local policy is applied, the border routers will choose their eBGP paths as best. They advertise that bestpath inside the ISP network. For a core router, there can be multiple paths to the same destination, but it will select only one path as best and use that path for forwarding. iBGP multipath load sharing adds the ability to enable load sharing among multiple equi-distant paths.

Configuring multiple iBGP best paths enables a router to evenly share the traffic destined for a particular site.

The iBGP Multipath Load Sharing feature functions similarly in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) with a service provider backbone.

For multiple paths to the same destination to be considered as multipaths, the following criteria must be met:

  • All attributes must be the same. The attributes include weight, local preference, autonomous system path (entire attribute and not just length), origin code, Multi Exit Discriminator (MED), and Interior Gateway Protocol (iGP) distance.
  • The next hop router for each multipath must be different.

Even if the criteria are met and multiple paths are considered multipaths, the BGP speaking router will still designate one of the multipaths as the best path and advertise this best path to its neighbors.

Accumulated Interior Gateway Protocol Attribute

The Accumulated Interior Gateway Protocol (AiGP)Attribute is an optional non-transitive BGP Path Attribute. The attribute type code for the AiGP Attribute is to be assigned by IANA. The value field of the AiGP Attribute is defined as a set of Type/Length/Value elements (TLVs). The AiGP TLV contains the Accumulated IGP Metric.

The AiGP feature is required in the 3107 network to simulate the current OSPF behavior of computing the distance associated with a path. OSPF/LDP carries the prefix/label information only in the local area. Then, BGP carries the prefix/lable to all the remote areas by redistributing the routes into BGP at area boundaries. The routes/labels are then advertised using LSPs. The next hop for the route is changed at each ABR to local router which removes the need to leak OSPF routes across area boundaries. The bandwidth available on each of the core links is mapped to OSPF cost, hence it is imperative that BGP carries this cost correctly between each of the PEs. This functionality is achieved by using the AiGP.

Per VRF and Per CE Label for IPv6 Provider Edge

The per VRF and per CE label for IPv6 feature makes it possible to save label space by allocating labels per default VRF or per CE nexthop.

All IPv6 Provider Edge (6PE) labels are allocated per prefix by default. Each prefix that belongs to a VRF instance is advertised with a single label, causing an additional lookup to be performed in the VRF forwarding table to determine the customer edge (CE) next hop for the packet.

However, use the label-allocation-mode command with the per-ce keyword or the per-vrf keyword to avoid the additional lookup on the PE router and conserve label space.

Use per-ce keyword to specify that the same label be used for all the routes advertised from a unique customer edge (CE) peer router. Use the per-vrf keyword to specify that the same label be used for all the routes advertised from a unique VRF.

IPv4 BGP-Policy Accounting on Cisco ASR 9000's A9K-SIP-700

Border Gateway Protocol (BGP) policy accounting measures and classifies IP traffic that is sent to, or received from, different peers. Policy accounting is enabled on an individual input or output interface basis. Counters based on parameters such as community list, autonomous system number, or autonomous system path are assigned to identify the IP traffic.

Using BGP policy accounting, you can account for traffic according to the route it traverses. Service providers can identify and account for all traffic by customer and bill accordingly.

For more information on BGP policy accounting and how to configure BGP policy accounting, refer the Implementing Cisco Express Forwarding module in Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Configuration Guide.

IPv6 Unicast Routing on Cisco ASR 9000's A9K-SIP-700

Cisco ASR 9000's A9K-SIP-700 provides complete Internet Protocol Version 6 (IPv6) unicast capability.

An IPv6 unicast address is an identifier for a single interface, on a single node. A packet that is sent to a unicast address is delivered to the interface identified by that address. Cisco IOS XR software supports the following IPv6 unicast address types:

  • Global aggregatable address
  • Site-local address
  • Link-local address
  • IPv4-compatible IPv6 address

For more information on IPv6 unicase addressing, refer the Implementing Network Stack IPv4 and IPv6 module in Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Configuration Guide.

IPv6 uRPF Support on Cisco ASR 9000's A9K-SIP-700

Unicast IPv6 Reverse Path Forwarding (uRPF) mitigates problems caused by the introduction of malformed or spoofed IP source addresses into a network by discarding IP packets that lack a verifiable IP source address. Unicast RPF does this by doing a reverse lookup in the Cisco Express Forwarding (CEF) table. Therefore, uRPF is possible only if CEF is enabled on the router.

Use the ipv6 verify unicast source reachable-via {any | rx} [allow-default] [allow-self-ping] command in interface configuration mode to enable IPV6 uRPF.

For more information on IPv6 uRPF, refer Implementing Cisco Express Forwarding module in Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Command Reference

Remove and Replace Private AS Numbers from AS Path in BGP

Private autonomous system numbers (ASNs) are used by Internet Service Providers (ISPs) and customer networks to conserve globally unique AS numbers. Private AS numbers cannot be used to access the global Internet because they are not unique. AS numbers appear in eBGP AS paths in routing updates. Removing private ASNs from the AS path is necessary if you have been using private ASNs and you want to access the global Internet.

Public AS numbers are assigned by InterNIC and are globally unique. They range from 1 to 64511. Private AS numbers are used to conserve globally unique AS numbers, and they range from 64512 to 65535. Private AS numbers cannot be leaked to a global BGP routing table because they are not unique, and BGP best path calculations require unique AS numbers. Therefore, it might be necessary to remove private AS numbers from an AS path before the routes are propagated to a BGP peer.

External BGP (eBGP) requires that globally unique AS numbers be used when routing to the global Internet. Using private AS numbers (which are not unique) would prevent access to the global Internet. The remove and replace private AS Numbers from AS Path in BGP feature allows routers that belong to a private AS to access the global Internet. A network administrator configures the routers to remove private AS numbers from the AS path contained in outgoing update messages and optionally, to replace those numbers with the ASN of the local router, so that the AS Path length remains unchanged.

The ability to remove and replace private AS numbers from the AS Path is implemented in the following ways:

  • The remove-private-as command removes private AS numbers from the AS path even if the path contains both public and private ASNs.
  • The remove-private-as command removes private AS numbers even if the AS path contains only private AS numbers. There is no likelihood of a 0-length AS path because this command can be applied to eBGP peers only, in which case the AS number of the local router is appended to the AS path.
  • The remove-private-as command removes private AS numbers even if the private ASNs appear before the confederation segments in the AS path.
  • The replace-as command replaces the private AS numbers being removed from the path with the local AS number, thereby retaining the same AS path length.

The feature can be applied to neighbors per address family (address family configuration mode). Therefore, you can apply the feature for a neighbor in one address family and not on another, affecting update messages on the outbound side for only the address family for which the feature is configured.

Use show bgp neighbors and show bgp update-group commands to verify that the that private AS numbers were removed or replaced.

Selective VRF Download

Selective VRF Download (SVD) feature enables the downloading of only those prefixes and labels to a line card that are actively required to forward traffic through the line card.

To meet the demand for a consolidated edge MSE platform, the number of VRFs, VRF interfaces, and the prefix capacity increase. Convergence timings differ in different line card engines. One of the major factors that determine convergence timing is the time taken to process and program a prefix and its associated data structures. A lesser number of prefixes and labels ensure better convergence timing. By enabling selective download of VRF routes, SVD increases scalability and reduces convergence problems in Layer 3 VPNs (L3VPNs).

For more information on selective VRF download, see the Cisco white paper, Selective Virtual Routing and Forwarding Table Download: A solution to increase Layer3 VPN scale at this URL http:/​/​www.cisco.com/​en/​US/​technologies/​collateral/​tk648/​tk365/​white_​paper_​c11-681649.html

Line Card Roles and Filters in Selective VRF Download

In a selective VRF download (SVD) context, line cards have these roles:

  • Core LC: a line card that has only core facing interfaces (interfaces that connect to other P/PEs)
  • Customer LC: a line card that has one or more customer facing interfaces (interfaces that connect to CEs in different VRFs)

The line cards handle these prefixes:

  • Local Prefix: a prefix that is received from a CE connected to the router in a configured VRF context
  • Remote Prefix: a prefix received from another PE and is imported to a configured VRF

These filters are applicable to each line card type:

  • A core LC needs all te local prefixes and VRF labels so that the label or IP forwarding, or both is set up correctly.
  • A customer LC needs both local and remote prefixes for all the VRFs to which it is connected, and for other VRFs which some connected VRFs have dependency. This is based on the import/export RT configuration; VRF ‘A’ may have imported routes from VRF ‘B’, so the imported route in VRF ‘A’ points to a next-hop that is in VRF ‘B’. For route resolution, VRF ‘B’ routes need to be downloaded to each line card that has a VRF ‘A’ interface.
  • If a line card is hosts both core facing and customer facing interfaces, then it does not need to do any filtering. All tables and all routes are present on such line cards. These line cards have a role called “standard”. All RPs and DRPs have the standard role.
  • To correctly resolve L3VPN routes, the IPv4 default table needs to be present an all nodes. However, if the line card does not have any IPv6 interface, it can filter out all IPv6 tables and routes. In such a case, the line card can be deemed “not interested” in the IPv6 AFI. Then it behaves as if IPv6 is not supported by it.

Selective VRF Download Disable

Selective VRF Download (SVD) functionality is disabled, by default. To enable SVD, configure the svd platform enable command in administrative configuration mode and reload the chassis using the reload location all command. To disable SVD that is already enabled, use the no svd platform enable command and reload the chassis using the reload location all command.

Calculating Routes Downloaded to Line Card with or without SVD

The number of routes that will be downloaded to the line card with or without selective VRF download option can be calculated by following the Total Tables and Routes Downloaded by Line Card Type table below.

This table summarizes the total routes and tables downloaded on the line cards of each SVD card type. Savings can be calculated by the difference between the numbers in the Without SVD row.

Table 2 Total Tables and Routes Downloaded by Line Card Type
Card Type Tables Downloaded Routes Downloaded
Customer (o+Y) (o+Y)R
Core n nxR
Without SVD n nR
  • n is the total number of VRFs present
  • o is the number of VRF directly provisioned/configured on the card, (n is greater than or equal to o)
  • R is routes per VRF
  • x is the ratio of SVD local: total routes
  • Y is the number of VRFs dependant on directly provisioned VRFs (o), (Y is greater than or equal to 0)

Here is an example calculation:

A customer has 100 VRFs configured on the system, with five line cards. For the IPv4 address family, four line cards are working as customer facing with equal VRF distribution, while one is core facing. Inter-table dependencies do not exist. In this example, n = 100, o = 25, x = 3/10, Y = 0, and R = 1000.

Number of routes downloaded:
  • Without SVD: (nR) = 100,000
  • On customer-facing card: (o+Y)R = 25,000
  • On core-facing card: (nxR) = 30,000

In this example, the SVD feature brings close to 70 per cent savings.

The total number of VRFs present (n) can be found by using the show cef tables summary location node-id command on the RSP card.
RP/0/RSP0/CPU0:router#show cef tables summary location 0/rsp0/cpu0

Role change timestamp     : Apr  3 07:21:46.759
Current Role              : Core
No. of times Eod received : 2
Eod received              : Apr  3 07:21:46.980

No. of Tables                 :       106
No. of Converged Tables       :       106
No. of Deleted Tables         :         0
No. of Bcdl Subscribed Tables :       106
No. of Marked Tables          :         0

The number of VRFs provisioned on the line card (o) is derived from the "No. Of Tables" field in the show cef tables summary location 0/0/cpu0. This provides the tables specific to the Linecard 0/0/cpu0.

The routes per VRF (R) can be found using the show cef tables location node-id command.
RP/0/RSP0/CPU0:router#show cef tables location 0/1/CPU0
Sat Apr  6 01:22:32.471 UTC

Codes:   L - SVD Local Routes, R - SVD Remote Routes
         T - Total Routes
         C - Table Converged,  D - Table Deleted
         M - Table Marked,     S - Table Subscribed

Table           Table ID             L          R           T C D M S
default         0xe0000000           9          3          23 Y N N Y
**nVSatellite   0xe0000010           1          0           6 Y N N Y
cdn             0xe0000011           0          0           5 Y N N Y
oir             0xe0000012           0          0           5 Y N N Y
vrf1            0xe0000013           3          1          11 Y N N Y

For the vrf "vrf1" the total routes is in the "T" column which is 11. So if the number of routes per VRF are not the same for all vrfs then total of "routes in all non-default" vrfs will have to be calculated and divided by the number of VRFs, to arrive at the Average Routes per VRF.

The ratio of SVD local: total routes (x) can be found using the number of SVD Local Routes and the number of Total Routes for a given VRF. For example, in the above sample output of show cef tables location 0/1/CPU0, in the L column, the number represents the Local Routes, and in the T column number represents Total routes in that Vrf. So ratio of L column to T column number will give the ratio for a given vrf. Again if the ratio is not same for all vrfs, it will have to be averaged out over all vrfs.

The number of VRFs dependant on directly provisioned VRFs (Y) will have to manually calculated because it depends on the router configuration. For example, if route import targets in Dependant VRF import from routes exported by other VRFs. A VRF is dependant if it depends on a nexthops being in some other VRF which is directly provisioned. There is no show command to automatically calculate Y, since it depends completely on the way router is configured to import routes in various VRFs.

BGP Accept Own

The BGP Accept Own feature enables handling of self-originated VPN routes, which a BGP speaker receives from a route-reflector (RR). A "self-originated" route is one which was originally advertized by the speaker itself. As per BGP protocol [RFC4271], a BGP speaker rejects advertisements that were originated by the speaker itself. However, the BGP Accept Own mechanism enables a router to accept the prefixes it has advertised, when reflected from a route-reflector that modifies certain attributes of the prefix. A special community called ACCEPT-OWN is attached to the prefix by the route-reflector, which is a signal to the receiving router to bypass the ORIGINATOR_ID and NEXTHOP/MP_REACH_NLRI check. Generally, the BGP speaker detects prefixes that are self-originated through the self-origination check (ORIGINATOR_ID, NEXTHOP/MP_REACH_NLRI) and drops the received updates. However, with the Accept Own community present in the update, the BGP speaker handles the route.

One of the applications of BGP Accept Own is auto-configuration of extranets within MPLS VPN networks. In an extranet configuration, routes present in one VRF is imported into another VRF on the same PE. Normally, the extranet mechanism requires that either the import-rt or the import policy of the extranet VRFs be modified to control import of the prefixes from another VRF. However, with Accept Own feature, the route-reflector can assert that control without the need for any configuration change on the PE. This way, the Accept Own feature provides a centralized mechanism for administering control of route imports between different VRFs.

BGP Accept Own is supported only for VPNv4 and VPNv6 address families in neighbor configuration mode.

Route-Reflector Handling Accept Own Community and RTs

The ACCEPT_OWN community is originated by the InterAS route-reflector (InterAS-RR) using an outbound route-policy. To minimize the propagation of prefixes with the ACCEPT_OWN community attribute, the attribute will be attached on the InterAS-RR using an outbound route-policy towards the originating PE. The InterAs-RR adds the ACCEPT-OWN community and modifies the set of RTs before sending the new Accept Own route to the attached PEs, including the originator, through intervening RRs. The route is modified via route-policy.

Accept Own Configuration Example

In this configuration example:
  • PE11 is configured with Customer VRF and Service VRF.
  • OSPF is used as the IGP.
  • VPNv4 unicast and VPNv6 unicast address families are enabled between the PE and RR neighbors and IPv4 and IPv6 are enabled between PE and CE neighbors.
The Accept Own configuration works as follows:
  1. CE1 originates prefix X.
  2. Prefix X is installed in customer VRF as (RD1:X).
  3. Prefix X is advertised to IntraAS-RR11 as (RD1:X, RT1).
  4. IntraAS-RR11 advertises X to InterAS-RR1 as (RD1:X, RT1).
  5. InterAS-RR1 attaches RT2 to prefix X on the inbound and ACCEPT_OWN community on the outbound and advertises prefix X to IntraAS-RR31.
  6. IntraAS-RR31 advertises X to PE11.
  7. PE11 installs X in Service VRF as (RD2:X,RT1, RT2, ACCEPT_OWN).

Remote PE: Handling of Accept Own Routes

Remote PEs (PEs other than the originator PE), performs bestpath calculation among all the comparable routes. The bestpath algorithm has been modified to prefer an Accept Own path over non-Accept Own path. The bestpath comparison occurs immediately before the IGP metric comparison. If the remote PE receives an Accept Own path from route-reflector 1 and a non-Accept Own path from route-reflector 2, and if the paths are otherwise identical, the Accept Own path is preferred. The import operates on the Accept Own path.

BGP DMZ Link Bandwidth for Unequal Cost Recursive Load Balancing

Border Gateway Protocol demilitarized zone (BGP DMZ) Link Bandwidth for Unequal Cost Recursive Load Balancing provides support for unequal cost load balancing for recursive prefixes on local node using BGP DMZ Link Bandwidth. The unequal load balance is achieved by using the dmz-link-bandwidth command in BGP Neighbor configuration mode and the bandwidth command in Interface configuration mode.

BFD Multihop Support for BGP

Bi-directional Forwarding Detection Multihop (BFD-MH) support is enabled for BGP. BFD Multihop establishes a BFD session between two addresses that may span multiple network hops. Cisco IOS XR Software BFD Multihop is based on RFC 5883. For more information on BFD Multihop, refer Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Configuration Guide and Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Command Reference.

BGP Multi-Instance/Multi-AS Support

Multi-Instance BGP is support for multiple BGP instances. Each BGP instance is a separate process running on the same or on a different RP/DRP node. The BGP instances do not share any prefix table between them. No need for a common adj-rib-in (bRIB) as is the case with distributed BGP. The BGP instances do not communicate with each other and do not set up peering with each other. Each individual instance can set up peering with another router independently.

Multi-AS BGP enables configuring each instance of a multi-instance BGP with a different AS number.

Multi-Instance/Multi-AS BGP provides these capabilities:
  • Mechanism to consolidate the services provided by multiple routers using a common routing infrastructure into a single IOS-XR router.
  • Mechanism to achieve AF isolation by configuring the different AFs in different BGP instances.
  • Means to achieve higher session scale by distributing the overall peering sessions between multiple instances.
  • Mechanism to achieve higher prefix scale (especially on a RR) by having different instances carrying different BGP tables.
  • Improved BGP convergence under certain scenarios.
  • All BGP functionalities including NSR are supported for all the instances.

BGP Prefix Origin Validation Based on RPKI

A BGP route associates an address prefix with a set of autonomous systems (AS) that identify the interdomain path the prefix has traversed in the form of BGP announcements. This set is represented as the AS_PATH attribute in BGP and starts with the AS that originated the prefix.

To help reduce well-known threats against BGP including prefix mis-announcing and monkey-in-the-middle attacks, one of the security requirements is the ability to validate the origination AS of BGP routes. The AS number claiming to originate an address prefix (as derived from the AS_PATH attribute of the BGP route) needs to be verified and authorized by the prefix holder.

The Resource Public Key Infrastructure (RPKI) is an approach to build a formally verifiable database of IP addresses and AS numbers as resources. The RPKI is a globally distributed database containing, among other things, information mapping BGP (internet) prefixes to their authorized origin-AS numbers. Routers running BGP can connect to the RPKI to validate the origin-AS of BGP paths.

BGP 3107 PIC Updates for Global Prefixes

The BGP 3107 PIC Updates for Global Prefixes feature supports Prefix Independent Convergence (PIC) updates for global IPv4 and IPv6 prefixes in an MPLS VPN provider network. This feature is based on RFC 3107 that describes using BGP to distribute MPLS labels for global IPv4 or IPv6 prefixes. This enables IGP to scale better and also provides PIC updates for fast convergence.

RFC 3107 enables routes and labels to be carried in BGP. When BGP is used to distribute a particular route, it can also be used to distribute an MPLS label that is mapped to that route. The label mapping information for a particular route is piggybacked in the same BGP Update message that is used to distribute the route itself. RFC 3107 allows filtering of Next-Hop Loops from OSPF and reduces labels advertised by LDP. This implementation significantly reduces OSPF and LDP database.

The 3107 PIC implementation supports the following address-families with additional-path configuration.
  • address-family ipv4 unicast
  • address-family ipv6 unicast
  • address-family vpnv4 unicast
  • address-family vpnv6 unicast

Note


The address-family l2vpn vpls-vpws does not support additional-path. Hence, the l2vpn service that uses address-family l2vpn vpls-vpws does not guarantee PIC convergence time.


The 3107 PIC implementation supports these Cisco IOS XR features:

  • PIC Edge for 3107
  • Traffic Engineering Fast-reroute (TE FRR)—Traffic convergence for core link failure is guaranteed within 50 milliseconds using verbatim tunnel.
  • L2VPN Service
  • L3VPN VPNv4 Service
  • 6 PE Service
  • 6 VPE Service
  • VPLS Service

BGP 3107 PIC Updates for Global Prefixes implementation uses a shared recursive Load Info (RLDI) forwarding object in place of a Light-Weight recursive (LW-RLDI) object. The RLDI is shared between multiple leaves, while the LW-RLDI is instantiated per leaf. Sharing helps in handling PIC updates since it will be prefix independent.

BGP Prefix Independent Convergence for RIB and FIB

BGP PIC for RIB and FIB adds support for static recursive as PE-CE and faster backup activation by using fast re-route trigger.

The BGP PIC for RIB and FIB feature supports:

  • FRR-like trigger for faster PE-CE link down detection, to further reduce the convergence time (Fast PIC-edge activation).
  • PIC-edge for static recursive routes.
  • BFD single-hop trigger for PIC-Edge without any explicit /32 static route configuration.
  • Recursive PIC activation at third level and beyond, on failure trigger at the first (IGP) level.
  • BGP path recursion constraints in FIB to ensure that FIB is in sync with BGP with respect to BGP next-hop resolution.

BGP Update Message Error Handling

The BGP UPDATE message error handling changes BGP behavior in handling error UPDATE messages to avoid session reset. Based on the approach described in IETF IDR I-D:draft-ietf-idr-error-handling, the Cisco IOS XR BGP UPDATE Message Error handling implementation classifies BGP update errors into various categories based on factors such as, severity, likelihood of occurrence of UPDATE errors, or type of attributes. Errors encountered in each category are handled according to the draft. Session reset will be avoided as much as possible during the error handling process. Error handling for some of the categories are controlled by configuration commands to enable or disable the default behavior.

According to the base BGP specification, a BGP speaker that receives an UPDATE message containing a malformed attribute is required to reset the session over which the offending attribute was received. This behavior is undesirable as a session reset would impact not only routes with the offending attribute, but also other valid routes exchanged over the session.

BGP Attribute Filtering

The BGP Attribute Filter feature checks integrity of BGP updates in BGP update messages and optimizes reaction when detecting invalid attributes. BGP Update message contains a list of mandatory and optional attributes. These attributes in the update message include MED, LOCAL_PREF, COMMUNITY etc. In some cases, if the attributes are malformed, there is a need to filter these attributes at the receiving end of the router. The BGP Attribute Filter functionality filters the attributes received in the incoming update message. The attribute filter can also be used to filter any attributes that may potentially cause undesirable behavior on the receiving router.

Some of the BGP updates are malformed due to wrong formatting of attributes such as the network layer reachability information (NLRI) or other fields in the update message. These malformed updates, when received, causes undesirable behavior on the receiving routers. Such undesirable behavior may be encountered during update message parsing or during re-advertisement of received NLRIs. In such scenarios, its better to filter these corrupted attributes at the receiving end.

BGP Attribute Filter Actions

The Attribute-filtering is configured by specifying a single or a range of attribute codes and an associated action. The allowed actions are:

  • " Treat-as-withdraw"— The associated IPv4-unicast or MP_REACH NLRIs, if present, are withdrawn from the neighbor's Adj-RIB-In.
  • "Discard Attribute"—The matching attributes alone are discarded and the rest of the Update message is processed normally.

When a received Update message contains one or more filtered attributes, the configured action is applied on the message. Optionally, the Update message is also stored to facilitate further debugging and a syslog message is generated on the console.

When an attribute matches the filter, further processing of the attribute is stopped and the corresponding action is taken.

Use the attribute-filter group command to enter Attribute-filter group command mode. Use the attribute command in attribute-filter group command mode to either discard an attribute or treat the update message as a "Withdraw" action.

BGP Error Handling and Attribute Filtering Syslog Messages

When a router receives a malformed update packet, an ios_msg of type ROUTING-BGP-3-MALFORM_UPDATE is printed on the console. This is rate limited to 1 message per minute across all neighbors. For malformed packets that result in actions "Discard Attribute" (A5) or "Local Repair" (A6), the ios_msg is printed only once per neighbor per action. This is irrespective of the number of malformed updates received since the neighbor last reached an "Established" state.

This is a sample BGP error handling syslog message:
%ROUTING-BGP-3-MALFORM_UPDATE : Malformed UPDATE message received from neighbor 13.0.3.50 - message length 90 bytes,
 error flags 0x00000840, action taken "TreatAsWithdraw". 
Error details: "Error 0x00000800, Field "Attr-missing", Attribute 1 (Flags 0x00, Length 0), Data []"

This is a sample BGP attribute filtering syslog message for the "discard attribute" action:
[4843.46]RP/0/0/CPU0:Aug 21 17:06:17.919 : bgp[1037]: %ROUTING-BGP-5-UPDATE_FILTERED : 
One or more attributes were filtered from UPDATE message received from neighbor 40.0.101.1 - message length 173 bytes,
 action taken "DiscardAttr".
 Filtering details: "Attribute 16 (Flags 0xc0): Action "DiscardAttr"". NLRIs: [IPv4 Unicast] 88.2.0.0/17

This is a sample BGP attribute filtering syslog message for the "treat-as-withdraw" action:
[391.01]RP/0/0/CPU0:Aug 20 19:41:29.243 : bgp[1037]: %ROUTING-BGP-5-UPDATE_FILTERED :
 One or more attributes were filtered from UPDATE message received from neighbor 40.0.101.1 - message length 166 bytes,
 action taken "TreatAsWdr".
 Filtering details: "Attribute 4 (Flags 0xc0): Action "TreatAsWdr"". NLRIs: [IPv4 Unicast] 88.2.0.0/17

BGP Link-State

BGP Link-State (LS) is an Address Family Identifier (AFI) and Sub-address Family Identifier (SAFI) defined to carry interior gateway protocol (IGP) link-state database through BGP. BGP LS delivers network topology information to topology servers and Application Layer Traffic Optimization (ALTO) servers. BGP LS allows policy-based control to aggregation, information-hiding, and abstraction. BGP LS supports IS-IS and OSPFv2.


Note


IGPs do not use BGP LS data from remote peers. BGP does not download the received BGP LS data to any other component on the router.

BGP Permanent Network

BGP permanent network feature supports static routing through BGP. BGP routes to IPv4 or IPv6 destinations (identified by a route-policy) can be administratively created and selectively advertised to BGP peers. These routes remain in the routing table until they are administratively removed.

A permanent network is used to define a set of prefixes as permanent, that is, there is only one BGP advertisement or withdrawal in upstream for a set of prefixes. For each network in the prefix-set, a BGP permanent path is created and treated as less preferred than the other BGP paths received from its peer. The BGP permanent path is downloaded into RIB when it is the best-path.

The permanent-network command in global address family configuration mode uses a route-policy to identify the set of prefixes (networks) for which permanent paths is to be configured. The advertise permanent-network command in neighbor address-family configuration mode is used to identify the peers to whom the permanent paths must be advertised. The permanent paths is always advertised to peers having the advertise permanent-network configuration, even if a different best-path is available. The permanent path is not advertised to peers that are not configured to receive permanent path.

The permanent network feature supports only prefixes in IPv4 unicast and IPv6 unicast address-families under the default Virtual Routing and Forwarding (VRF).

Restrictions

These restrictions apply while configuring the permanent network:

  • Permanent network prefixes must be specified by the route-policy on the global address family.
  • You must configure the permanent network with route-policy in global address family configuration mode and then configure it on the neighbor address family configuration mode.
  • When removing the permanent network configuration, remove the configuration in the neighbor address family configuration mode and then remove it from the global address family configuration mode.

BGP-RIB Feedback Mechanism for Update Generation

The Border Gateway Protocol-Routing Information Base (BGP-RIB) feedback mechanism for update generation feature avoids premature route advertisements and subsequent packet loss in a network. This mechanism ensures that routes are installed locally, before they are advertised to a neighbor.

BGP waits for feedback from RIB indicating that the routes that BGP installed in RIB are installed in forwarding information base (FIB) before BGP sends out updates to the neighbors. RIB uses the the BCDL feedback mechanism to determine which version of the routes have been consumed by FIB, and updates the BGP with that version. BGP will send out updates of only those routes that have versions up to the version that FIB has installed. This selective update ensures that BGP does not send out premature updates resulting in attracting traffic even before the data plane is programmed after router reload, LC OIR, or flap of a link where an alternate path is made available.

To configure BGP to wait for feedback from RIB indicating that the routes that BGP installed in RIB are installed in FIB, before BGP sends out updates to neighbors, use the update wait-install command in router address-family IPv4 or router address-family VPNv4 configuration mode. The show bgp, show bgp neighbors, and show bgp process performance-statistics commands display the information from update wait-install configuration.

BGP VRF Dynamic Route Leaking

The Border Gateway Protocol (BGP) dynamic route leaking feature provides the ability to import routes between the default-vrf (Global VRF) and any other non-default VRF, to provide connectivity between a global and a VPN host. The import process installs the Internet route in a VRF table or a VRF route in the Internet table, providing connectivity.

The dynamic route leaking is enabled by:
  • Importing from default-VRF to non-default-VRF, using the import from default-vrf route-policy route-policy-name [advertise-as-vpn] command in VRF address-family configuration mode. If the advertise-as-vpn option is configured, the paths imported from the default-VRF to the non-default-VRF are advertised to the PEs as well as to the CEs. If the advertise-as-vpn option is not configured, the paths imported from the default-VRF to the non-default-VRF are not advertised to the PE. However, the paths are still advertised to the CEs.
  • Importing from non-default-VRF to default VRF, using the export to default-vrf route-policy route-policy-name command in VRF address-family configuration mode.

A route-policy is mandatory to filter the imported routes. This reduces the risk of unintended import of routes between the Internet table and the VRF tables and the corresponding security issues.

There is no hard limit on the number of prefixes that can be imported. The import creates a new prefix in the destination VRF, which increases the total number of prefixes and paths. However, each VRF importing global routes adds workload equivalent to a neighbor receiving the global table. This is true even if the user filters out all but a few prefixes. Hence, importing five to ten VRFs is ideal.

User Defined Martian Check

The Cisco IOS XR Software Release 5.1.0 allows disabling the Martian check for these IP address prefixes:

  • IPv4 address prefixes
    • 0.0.0.0/8
    • 127.0.0.0/8
    • 224.0.0.0/4
  • IPv6 address prefixes
    • ::
    • ::0002 - ::ffff
    • ::ffff:a.b.c.d
    • fe80:xxxx
    • ffxx:xxxx

How to Implement BGP

Enabling BGP Routing

Perform this task to enable BGP routing and establish a BGP routing process. Configuring BGP neighbors is included as part of enabling BGP routing.


Note


At least one neighbor and at least one address family must be configured to enable BGP routing. At least one neighbor with both a remote AS and an address family must be configured globally using the address family and remote as commands.


Before You Begin

BGP must be able to obtain a router identifier (for example, a configured loopback address). At least, one address family must be configured in the BGP router configuration and the same address family must also be configured under the neighbor.


Note


If the neighbor is configured as an external BGP (eBGP) peer, you must configure an inbound and outbound route policy on the neighbor using the route-policy command.


SUMMARY STEPS

    1.    configure

    2.    route-policy route-policy-name

    3.    end-policy

    4.    Use the commit or end command.

    5.    configure

    6.    router bgp as-number

    7.    bgp router-id ip-address

    8.    address-family { ipv4 | ipv6 } unicast

    9.    exit

    10.    neighbor ip-address

    11.    remote-as as-number

    12.    address-family { ipv4 | ipv6 } unicast

    13.    route-policy route-policy-name { in | out }

    14.    Use the commit or end command.


DETAILED STEPS
      Command or Action Purpose
    Step 1 configure


    Example:
    RP/0/RSP0/CPU0:router# configure
     

    Enters global configuration mode.

     
    Step 2 route-policy route-policy-name


    Example:
    RP/0/RSP0/CPU0:router(config)# route-policy drop-as-1234
      RP/0/RSP0/CPU0:router(config-rpl)# if as-path passes-through '1234' then
      RP/0/RSP0/CPU0:router(config-rpl)# apply check-communities
      RP/0/RSP0/CPU0:router(config-rpl)# else
      RP/0/RSP0/CPU0:router(config-rpl)# pass
      RP/0/RSP0/CPU0:router(config-rpl)# endif
      
     

    (Optional) Creates a route policy and enters route policy configuration mode, where you can define the route policy.

     
    Step 3 end-policy


    Example:
    RP/0/RSP0/CPU0:router(config-rpl)# end-policy
     

    (Optional) Ends the definition of a route policy and exits route policy configuration mode.

     
    Step 4 Use the commit or end command.  

    commit—Saves the configuration changes, and remains within the configuration session.

    end—Prompts user to take one of these actions:
    • Yes— Saves configuration changes and exits the configuration session.
    • No—Exits the configuration session without committing the configuration changes.
    • Cancel—Remains in the configuration mode, without committing the configuration changes.
     
    Step 5 configure


    Example:
    RP/0/RSP0/CPU0:router# configure
     

    Enters global configuration mode.

     
    Step 6 router bgp as-number


    Example:
    RP/0/RSP0/CPU0:router(config)# router bgp 120
     

    Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

     
    Step 7 bgp router-id ip-address


    Example:
    RP/0/RSP0/CPU0:router(config-bgp)# bgp router-id 192.168.70.24
     

    Configures the local router with a specified router ID.

     
    Step 8 address-family { ipv4 | ipv6 } unicast


    Example:
    RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
     

    Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

    To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

     
    Step 9 exit


    Example:
    RP/0/RSP0/CPU0:router(config-bgp-af)# exit
     

    Exits the current configuration mode.

     
    Step 10 neighbor ip-address


    Example:
    RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
     

    Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

     
    Step 11 remote-as as-number


    Example:
    RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002
     

    Creates a neighbor and assigns a remote autonomous system number to it.

     
    Step 12 address-family { ipv4 | ipv6 } unicast


    Example:
    RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
     

    Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

    To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

     
    Step 13 route-policy route-policy-name { in | out }


    Example:
    RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy drop-as-1234 in
     

    (Optional) Applies the specified policy to inbound IPv4 unicast routes.

     
    Step 14 Use the commit or end command.  

    commit—Saves the configuration changes, and remains within the configuration session.

    end—Prompts user to take one of these actions:
    • Yes— Saves configuration changes and exits the configuration session.
    • No—Exits the configuration session without committing the configuration changes.
    • Cancel—Remains in the configuration mode, without committing the configuration changes.
     

    Configuring a Routing Domain Confederation for BGP

    Perform this task to configure the routing domain confederation for BGP. This includes specifying a confederation identifier and autonomous systems that belong to the confederation.

    Configuring a routing domain confederation reduces the internal BGP (iBGP) mesh by dividing an autonomous system into multiple autonomous systems and grouping them into a single confederation. Each autonomous system is fully meshed within itself and has a few connections to another autonomous system in the same confederation. The confederation maintains the next hop and local preference information, and that allows you to retain a single Interior Gateway Protocol (IGP) for all autonomous systems. To the outside world, the confederation looks like a single autonomous system.

    SUMMARY STEPS

      1.    configure

      2.    router bgp as-number

      3.    bgp confederation identifier as-number

      4.    bgp confederation peers as-number

      5.    Use the commit or end command.


    DETAILED STEPS
        Command or Action Purpose
      Step 1 configure


      Example:
      RP/0/RSP0/CPU0:router# configure
       

      Enters global configuration mode.

       
      Step 2 router bgp as-number


      Example:
      RP/0/RSP0/CPU0:router# router bgp 120
       

      Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

       
      Step 3 bgp confederation identifier as-number


      Example:
      RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation identifier 5
       

      Specifies a BGP confederation identifier.

       
      Step 4 bgp confederation peers as-number


      Example:
      RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation peers 1091
        RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation peers 1092
        RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation peers 1093
        RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation peers 1094
        RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation peers 1095
        RP/0/RSP0/CPU0:router(config-bgp)# bgp confederation peers 1096
        
       

      Specifies that the BGP autonomous systems belong to a specified BGP confederation identifier. You can associate multiple AS numbers to the same confederation identifier, as shown in the example.

       
      Step 5 Use the commit or end command.  

      commit—Saves the configuration changes, and remains within the configuration session.

      end—Prompts user to take one of these actions:
      • Yes— Saves configuration changes and exits the configuration session.
      • No—Exits the configuration session without committing the configuration changes.
      • Cancel—Remains in the configuration mode, without committing the configuration changes.
       

      Resetting an eBGP Session Immediately Upon Link Failure

      By default, if a link goes down, all BGP sessions of any directly adjacent external peers are immediately reset. Use the bgp fast-external-fallover disable command to disable automatic resetting. Turn the automatic reset back on using the no bgp fast-external-fallover disable command.

      eBGP sessions flap when the node reaches 3500 eBGP sessions with BGP timer values set as 10 and 30. To support more than 3500 eBGP sessions, increase the packet rate by using the lpts pifib hardware police location location-id command. Following is a sample configuration to increase the eBGP sessions:
      RP/0/RSP0/CPU0:router#configure 
      RP/0/RSP0/CPU0:router(config)#lpts pifib hardware police location 0/2/CPU0
      RP/0/RSP0/CPU0:router(config-pifib-policer-per-node)#flow bgp configured rate 4000
      RP/0/RSP0/CPU0:router(config-pifib-policer-per-node)#flow bgp known rate 4000
      RP/0/RSP0/CPU0:router(config-pifib-policer-per-node)#flow bgp default rate 4000
      RP/0/RSP0/CPU0:router(config-pifib-policer-per-node)#commit

      Logging Neighbor Changes

      Logging neighbor changes is enabled by default. Use the log neighbor changes disable command to turn off logging. The no log neighbor changes disable command can also be used to turn logging back on if it has been disabled.

      Adjusting BGP Timers

      Perform this task to set the timers for BGP neighbors.

      BGP uses certain timers to control periodic activities, such as the sending of keepalive messages and the interval after which a neighbor is assumed to be down if no messages are received from the neighbor during the interval. The values set using the timers bgp command in router configuration mode can be overridden on particular neighbors using the timers command in the neighbor configuration mode.

      SUMMARY STEPS

        1.    configure

        2.    router bgp as-number

        3.    timers bgp keepalive hold-time

        4.    neighbor ip-address

        5.    timers keepalive hold-time

        6.    Use the commit or end command.


      DETAILED STEPS
          Command or Action Purpose
        Step 1 configure


        Example:
        RP/0/RSP0/CPU0:router# configure
         

        Enters global configuration mode.

         
        Step 2 router bgp as-number


        Example:
        RP/0/RSP0/CPU0:router(config)# router bgp 123
         

        Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

         
        Step 3 timers bgp keepalive hold-time


        Example:
        RP/0/RSP0/CPU0:router(config-bgp)# timers bgp 30 90
         

        Sets a default keepalive time and a default hold time for all neighbors.

         
        Step 4 neighbor ip-address


        Example:
        RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
         

        Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

         
        Step 5 timers keepalive hold-time


        Example:
        RP/0/RSP0/CPU0:router(config-bgp-nbr)# timers 60 220
         

        (Optional) Sets the keepalive timer and the hold-time timer for the BGP neighbor.

         
        Step 6 Use the commit or end command.  

        commit—Saves the configuration changes, and remains within the configuration session.

        end—Prompts user to take one of these actions:
        • Yes— Saves configuration changes and exits the configuration session.
        • No—Exits the configuration session without committing the configuration changes.
        • Cancel—Remains in the configuration mode, without committing the configuration changes.
         

        Changing the BGP Default Local Preference Value

        Perform this task to set the default local preference value for BGP paths.

        SUMMARY STEPS

          1.    configure

          2.    router bgp as-number

          3.    bgp default local-preference value

          4.    Use the commit or end command.


        DETAILED STEPS
            Command or Action Purpose
          Step 1 configure


          Example:
          RP/0/RSP0/CPU0:router# configure
           

          Enters global configuration mode.

           
          Step 2 router bgp as-number


          Example:
          RP/0/RSP0/CPU0:router(config)# router bgp 120
           

          Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

           
          Step 3 bgp default local-preference value


          Example:
          RP/0/RSP0/CPU0:router(config-bgp)# bgp default local-preference 200
           

          Sets the default local preference value from the default of 100, making it either a more preferable path (over 100) or less preferable path (under 100).

           
          Step 4 Use the commit or end command.  

          commit—Saves the configuration changes, and remains within the configuration session.

          end—Prompts user to take one of these actions:
          • Yes— Saves configuration changes and exits the configuration session.
          • No—Exits the configuration session without committing the configuration changes.
          • Cancel—Remains in the configuration mode, without committing the configuration changes.
           

          Configuring the MED Metric for BGP

          Perform this task to set the multi exit discriminator (MED) to advertise to peers for routes that do not already have a metric set (routes that were received with no MED attribute).

          SUMMARY STEPS

            1.    configure

            2.    router bgp as-number

            3.    default-metric value

            4.    Use the commit or end command.


          DETAILED STEPS
              Command or Action Purpose
            Step 1 configure


            Example:
            RP/0/RSP0/CPU0:router# configure
             

            Enters global configuration mode.

             
            Step 2 router bgp as-number


            Example:
            RP/0/RSP0/CPU0:router(config)# router bgp 120
             

            Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

             
            Step 3 default-metric value


            Example:
            RP/0/RSP0/CPU0:router(config-bgp)# default metric 10
             

            Sets the default metric, which is used to set the MED to advertise to peers for routes that do not already have a metric set (routes that were received with no MED attribute).

             
            Step 4 Use the commit or end command.  

            commit—Saves the configuration changes, and remains within the configuration session.

            end—Prompts user to take one of these actions:
            • Yes— Saves configuration changes and exits the configuration session.
            • No—Exits the configuration session without committing the configuration changes.
            • Cancel—Remains in the configuration mode, without committing the configuration changes.
             

            Configuring BGP Weights

            Perform this task to assign a weight to routes received from a neighbor. A weight is a number that you can assign to a path so that you can control the best-path selection process. If you have particular neighbors that you want to prefer for most of your traffic, you can use the weight command to assign a higher weight to all routes learned from that neighbor.

            Before You Begin

            Note


            The clear bgp command must be used for the newly configured weight to take effect.


            SUMMARY STEPS

              1.    configure

              2.    router bgp as-number

              3.    neighbor ip-address

              4.    remote-as as-number

              5.    address-family { ipv4 | ipv6 } unicast

              6.    weight weight-value

              7.    Use the commit or end command.


            DETAILED STEPS
                Command or Action Purpose
              Step 1 configure


              Example:
              RP/0/RSP0/CPU0:router# configure
               

              Enters global configuration mode.

               
              Step 2 router bgp as-number


              Example:
              RP/0/RSP0/CPU0:router(config)# router bgp 120
               

              Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

               
              Step 3 neighbor ip-address


              Example:
              RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
               

              Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

               
              Step 4 remote-as as-number


              Example:
              RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002 
               

              Creates a neighbor and assigns a remote autonomous system number to it.

               
              Step 5 address-family { ipv4 | ipv6 } unicast


              Example:
              RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
               

              Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

              To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

               
              Step 6 weight weight-value


              Example:
              RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# weight 41150
               

              Assigns a weight to all routes learned through the neighbor.

               
              Step 7 Use the commit or end command.  

              commit—Saves the configuration changes, and remains within the configuration session.

              end—Prompts user to take one of these actions:
              • Yes— Saves configuration changes and exits the configuration session.
              • No—Exits the configuration session without committing the configuration changes.
              • Cancel—Remains in the configuration mode, without committing the configuration changes.
               

              Tuning the BGP Best-Path Calculation

              Perform this task to change the default BGP best-path calculation behavior.

              SUMMARY STEPS

                1.    configure

                2.    router bgp as-number

                3.    bgp bestpath med missing-as-worst

                4.    bgp bestpath med always

                5.    bgp bestpath med confed

                6.    bgp bestpath as-path ignore

                7.    bgp bestpath compare-routerid

                8.    Use the commit or end command.


              DETAILED STEPS
                  Command or Action Purpose
                Step 1 configure


                Example:
                RP/0/RSP0/CPU0:router# configure
                 

                Enters global configuration mode.

                 
                Step 2 router bgp as-number


                Example:
                RP/0/RSP0/CPU0:router(config)# router bgp 126
                 

                Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                 
                Step 3 bgp bestpath med missing-as-worst


                Example:
                RP/0/RSP0/CPU0:router(config-bgp)# bgp bestpath med missing-as-worst
                 

                Directs the BGP software to consider a missing MED attribute in a path as having a value of infinity, making this path the least desirable path.

                 
                Step 4 bgp bestpath med always


                Example:
                RP/0/RSP0/CPU0:router(config-bgp)# bgp bestpath med always
                 

                Configures the BGP speaker in the specified autonomous system to compare MEDs among all the paths for the prefix, regardless of the autonomous system from which the paths are received.

                 
                Step 5 bgp bestpath med confed


                Example:
                RP/0/RSP0/CPU0:router(config-bgp)# bgp bestpath med confed
                 

                Enables BGP software to compare MED values for paths learned from confederation peers.

                 
                Step 6 bgp bestpath as-path ignore


                Example:
                RP/0/RSP0/CPU0:router(config-bgp)# bgp bestpath as-path ignore
                 

                Configures the BGP software to ignore the autonomous system length when performing best-path selection.

                 
                Step 7 bgp bestpath compare-routerid


                Example:
                RP/0/RSP0/CPU0:router(config-bgp)# bgp bestpath compare-routerid
                 

                Configure the BGP speaker in the autonomous system to compare the router IDs of similar paths.

                 
                Step 8 Use the commit or end command.  

                commit—Saves the configuration changes, and remains within the configuration session.

                end—Prompts user to take one of these actions:
                • Yes— Saves configuration changes and exits the configuration session.
                • No—Exits the configuration session without committing the configuration changes.
                • Cancel—Remains in the configuration mode, without committing the configuration changes.
                 

                Indicating BGP Back-door Routes

                Perform this task to set the administrative distance on an external Border Gateway Protocol (eBGP) route to that of a locally sourced BGP route, causing it to be less preferred than an Interior Gateway Protocol (IGP) route.

                SUMMARY STEPS

                  1.    configure

                  2.    router bgp as-number

                  3.    address-family { ipv4 | ipv6 } unicast

                  4.    network { ip-address / prefix-length | ip-address mask } backdoor

                  5.    Use the commit or end command.


                DETAILED STEPS
                    Command or Action Purpose
                  Step 1 configure


                  Example:
                  RP/0/RSP0/CPU0:router# configure
                   

                  Enters global configuration mode.

                   
                  Step 2 router bgp as-number


                  Example:
                  RP/0/RSP0/CPU0:router(config)# router bgp 120
                   

                  Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                   
                  Step 3 address-family { ipv4 | ipv6 } unicast


                  Example:
                  RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                   

                  Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                  To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                   
                  Step 4 network { ip-address / prefix-length | ip-address mask } backdoor


                  Example:
                  RP/0/RSP0/CPU0:router(config-bgp-af)# network 172.20.0.0/16 
                   

                  Configures the local router to originate and advertise the specified network.

                   
                  Step 5 Use the commit or end command.  

                  commit—Saves the configuration changes, and remains within the configuration session.

                  end—Prompts user to take one of these actions:
                  • Yes— Saves configuration changes and exits the configuration session.
                  • No—Exits the configuration session without committing the configuration changes.
                  • Cancel—Remains in the configuration mode, without committing the configuration changes.
                   

                  Configuring Aggregate Addresses

                  Perform this task to create aggregate entries in a BGP routing table.

                  SUMMARY STEPS

                    1.    configure

                    2.    router bgp as-number

                    3.    address-family { ipv4 | ipv6 } unicast

                    4.    aggregate-address address/mask-length [ as-set ] [ as-confed-set ] [ summary-only ] [ route-policy route-policy-name ]

                    5.    Use the commit or end command.


                  DETAILED STEPS
                      Command or Action Purpose
                    Step 1 configure


                    Example:
                    RP/0/RSP0/CPU0:router# configure
                     

                    Enters global configuration mode.

                     
                    Step 2 router bgp as-number


                    Example:
                    RP/0/RSP0/CPU0:router(config)# router bgp 120
                     

                    Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                     
                    Step 3 address-family { ipv4 | ipv6 } unicast


                    Example:
                    RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                     

                    Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                    To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                     
                    Step 4 aggregate-address address/mask-length [ as-set ] [ as-confed-set ] [ summary-only ] [ route-policy route-policy-name ]


                    Example:
                    RP/0/RSP0/CPU0:router(config-bgp-af)# aggregate-address 10.0.0.0/8 as-set
                     

                    Creates an aggregate address. The path advertised for this route is an autonomous system set consisting of all elements contained in all paths that are being summarized.

                    • The as-set keyword generates autonomous system set path information and community information from contributing paths.
                    • The as-confed-set keyword generates autonomous system confederation set path information from contributing paths.
                    • The summary-only keyword filters all more specific routes from updates.
                    • The route-policy route-policy-name keyword and argument specify the route policy used to set the attributes of the aggregate route.
                     
                    Step 5 Use the commit or end command.  

                    commit—Saves the configuration changes, and remains within the configuration session.

                    end—Prompts user to take one of these actions:
                    • Yes— Saves configuration changes and exits the configuration session.
                    • No—Exits the configuration session without committing the configuration changes.
                    • Cancel—Remains in the configuration mode, without committing the configuration changes.
                     

                    Redistributing iBGP Routes into IGP

                    Perform this task to redistribute iBGP routes into an Interior Gateway Protocol (IGP), such as Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF).


                    Note


                    Use of the bgp redistribute-internal command requires the clear route * command to be issued to reinstall all BGP routes into the IP routing table.



                    Caution


                    Redistributing iBGP routes into IGPs may cause routing loops to form within an autonomous system. Use this command with caution.


                    SUMMARY STEPS

                      1.    configure

                      2.    router bgp as-number

                      3.    bgp redistribute-internal

                      4.    Use the commit or end command.


                    DETAILED STEPS
                        Command or Action Purpose
                      Step 1 configure


                      Example:
                      RP/0/RSP0/CPU0:router# configure
                       

                      Enters global configuration mode.

                       
                      Step 2 router bgp as-number


                      Example:
                      RP/0/RSP0/CPU0:router(config)# router bgp 120
                       

                      Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                       
                      Step 3 bgp redistribute-internal


                      Example:
                      RP/0/RSP0/CPU0:router(config-bgp)# bgp redistribute-internal
                       

                      Allows the redistribution of iBGP routes into an IGP, such as IS-IS or OSPF.

                       
                      Step 4 Use the commit or end command.  

                      commit—Saves the configuration changes, and remains within the configuration session.

                      end—Prompts user to take one of these actions:
                      • Yes— Saves configuration changes and exits the configuration session.
                      • No—Exits the configuration session without committing the configuration changes.
                      • Cancel—Remains in the configuration mode, without committing the configuration changes.
                       

                      Redistributing Prefixes into Multiprotocol BGP

                      Perform this task to redistribute prefixes from another protocol into multiprotocol BGP.

                      Redistribution is the process of injecting prefixes from one routing protocol into another routing protocol. This task shows how to inject prefixes from another routing protocol into multiprotocol BGP. Specifically, prefixes that are redistributed into multiprotocol BGP using the redistribute command are injected into the unicast database, the multicast database, or both.

                      SUMMARY STEPS

                        1.    configure

                        2.    router bgp as-number

                        3.    address-family { ipv4 | ipv6 } unicast

                        4.    Do one of the following:

                        • redistribute connected [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute eigrp process-id [ match { external | internal }] [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute isis process-id [ level { 1 | 1-inter-area | 2 }] [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute ospf process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]]} [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute ospfv3 process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]]} [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute rip [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute static [ metric metric-value ] [ route-policy route-policy-name ]

                        5.    Use the commit or end command.


                      DETAILED STEPS
                          Command or Action Purpose
                        Step 1 configure


                        Example:
                        RP/0/RSP0/CPU0:router# configure
                         

                        Enters global configuration mode.

                         
                        Step 2 router bgp as-number


                        Example:
                        RP/0/RSP0/CPU0:router(config)# router bgp 120
                         

                        Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                         
                        Step 3 address-family { ipv4 | ipv6 } unicast


                        Example:
                        RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                         

                        Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                        To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                         
                        Step 4 Do one of the following:
                        • redistribute connected [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute eigrp process-id [ match { external | internal }] [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute isis process-id [ level { 1 | 1-inter-area | 2 }] [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute ospf process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]]} [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute ospfv3 process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]]} [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute rip [ metric metric-value ] [ route-policy route-policy-name ]
                        • redistribute static [ metric metric-value ] [ route-policy route-policy-name ]


                        Example:
                        RP/0/RSP0/CPU0:router(config-bgp-af)# redistribute ospf 110
                         

                        Causes routes from the specified instance to be redistributed into BGP.

                         
                        Step 5 Use the commit or end command.  

                        commit—Saves the configuration changes, and remains within the configuration session.

                        end—Prompts user to take one of these actions:
                        • Yes— Saves configuration changes and exits the configuration session.
                        • No—Exits the configuration session without committing the configuration changes.
                        • Cancel—Remains in the configuration mode, without committing the configuration changes.
                         

                        Configuring BGP Route Dampening

                        Perform this task to configure and monitor BGP route dampening.

                        SUMMARY STEPS

                          1.    configure

                          2.    router bgp as-number

                          3.    address-family { ipv4 | ipv6 } unicast

                          4.    bgp dampening [ half-life [ reuse suppress max-suppress-time ] | route-policy route-policy-name ]

                          5.    Use the commit or end command.

                          6.    show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics

                          7.    show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics regexp regular-expression

                          8.    show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | labeled all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics route-policy route-policy-name

                          9.    show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | labeled all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics { ip-address { mask | /prefix-length }}

                          10.    show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics { ip-address [{ mask | /prefix-length } [ longer-prefixes ]]}

                          11.    clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics

                          12.    clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast }} flap-statistics regexp regular-expression

                          13.    clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics route-policy route-policy-name

                          14.    clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics network / mask-length

                          15.    clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics ip-address / mask-length

                          16.    show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | labeled all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] dampened-paths

                          17.    clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } dampening [ ip-address / mask-length ]


                        DETAILED STEPS
                            Command or Action Purpose
                          Step 1 configure


                          Example:
                          RP/0/RSP0/CPU0:router# configure
                           

                          Enters global configuration mode.

                           
                          Step 2 router bgp as-number


                          Example:
                          RP/0/RSP0/CPU0:router(config)# router bgp 120
                           

                          Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                           
                          Step 3 address-family { ipv4 | ipv6 } unicast


                          Example:
                          RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                           

                          Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                          To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                           
                          Step 4 bgp dampening [ half-life [ reuse suppress max-suppress-time ] | route-policy route-policy-name ]


                          Example:
                          RP/0/RSP0/CPU0:router(config-bgp-af)# bgp dampening 30 1500 10000 120
                           

                          Configures BGP dampening for the specified address family.

                           
                          Step 5 Use the commit or end command.  

                          commit—Saves the configuration changes, and remains within the configuration session.

                          end—Prompts user to take one of these actions:
                          • Yes— Saves configuration changes and exits the configuration session.
                          • No—Exits the configuration session without committing the configuration changes.
                          • Cancel—Remains in the configuration mode, without committing the configuration changes.
                           
                          Step 6 show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics


                          Example:
                          RP/0/RSP0/CPU0:router# show bgp flap statistics
                           

                          Displays BGP flap statistics.

                           
                          Step 7 show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics regexp regular-expression


                          Example:
                          RP/0/RSP0/CPU0:router# show bgp flap-statistics regexp _1$
                           

                          Displays BGP flap statistics for all paths that match the regular expression.

                           
                          Step 8 show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | labeled all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics route-policy route-policy-name


                          Example:
                          RP/0/RSP0/CPU0:router(config)# show bgp flap-statistics route-policy policy_A
                           

                          Displays BGP flap statistics for the specified route policy.

                           
                          Step 9 show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | labeled all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics { ip-address { mask | /prefix-length }}


                          Example:
                          RP/0/RSP0/CPU0:router# show bgp flap-statistics 172.20.1.1
                           

                          Displays BGP flap for the specified prefix.

                           
                          Step 10 show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] flap-statistics { ip-address [{ mask | /prefix-length } [ longer-prefixes ]]}


                          Example:
                          RP/0/RSP0/CPU0:router# show bgp flap-statistics 172.20.1.1 longer-prefixes
                           

                          Displays BGP flap statistics for more specific entries for the specified IP address.

                           
                          Step 11 clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics


                          Example:
                          RP/0/RSP0/CPU0:router# clear bgp all all flap-statistics 
                           

                          Clears BGP flap statistics for all routes.

                           
                          Step 12 clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast }} flap-statistics regexp regular-expression


                          Example:
                          RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast flap-statistics regexp _1$
                           

                          Clears BGP flap statistics for all paths that match the specified regular expression.

                           
                          Step 13 clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics route-policy route-policy-name


                          Example:
                          RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast flap-statistics route-policy policy_A
                           

                          Clears BGP flap statistics for the specified route policy.

                           
                          Step 14 clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics network / mask-length


                          Example:
                          RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast flap-statistics 192.168.40.0/24
                           

                          Clears BGP flap statistics for the specified network.

                           
                          Step 15 clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } flap-statistics ip-address / mask-length


                          Example:
                          RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast flap-statistics 172.20.1.1
                           

                          Clears BGP flap statistics for routes received from the specified neighbor.

                           
                          Step 16 show bgp [ ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | labeled all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast [ rd rd-address ] | vrf { vrf-name | all } [ ipv4 { unicast | labeled-unicast } | ipv6 unicast ]] dampened-paths


                          Example:
                          RP/0/RSP0/CPU0:router# show bgp dampened paths
                           

                          Displays the dampened routes, including the time remaining before they are unsuppressed.

                           
                          Step 17 clear bgp { ipv4 { unicast | multicast | labeled-unicast | all } | ipv6 unicast | all { unicast | multicast | all | labeled-unicast } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 { unicast | labeled-unicast } | ipv6 unicast } } dampening [ ip-address / mask-length ]


                          Example:
                          RP/0/RSP0/CPU0:router# clear bgp dampening
                           

                          Clears route dampening information and unsuppresses the suppressed routes.

                          Caution   

                          Always use the clear bgp dampening command for an individual address-family. The all option for address-families with clear bgp dampening should never be used during normal functioning of the system. For example, use clear bgp ipv4 unicast dampening prefix x.x.x./y

                           

                          Applying Policy When Updating the Routing Table

                          Perform this task to apply a routing policy to routes being installed into the routing table.

                          Before You Begin

                          See the Implementing Routing Policy on Cisco ASR 9000 Series Router module of Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide (this publication) for a list of the supported attributes and operations that are valid for table policy filtering.

                          SUMMARY STEPS

                            1.    configure

                            2.    router bgp as-number

                            3.    address-family { ipv4 | ipv6 } unicast

                            4.    table-policy policy-name

                            5.    Use the commit or end command.


                          DETAILED STEPS
                              Command or Action Purpose
                            Step 1 configure


                            Example:
                            RP/0/RSP0/CPU0:router# configure
                             

                            Enters global configuration mode.

                             
                            Step 2 router bgp as-number


                            Example:
                            RP/0/RSP0/CPU0:router(config)# router bgp 120.6
                             

                            Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                             
                            Step 3 address-family { ipv4 | ipv6 } unicast


                            Example:
                            RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                             

                            Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                            To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                             
                            Step 4 table-policy policy-name


                            Example:
                            RP/0/RSP0/CPU0:router(config-bgp-af)# table-policy tbl-plcy-A
                             

                            Applies the specified policy to routes being installed into the routing table.

                             
                            Step 5 Use the commit or end command.  

                            commit—Saves the configuration changes, and remains within the configuration session.

                            end—Prompts user to take one of these actions:
                            • Yes— Saves configuration changes and exits the configuration session.
                            • No—Exits the configuration session without committing the configuration changes.
                            • Cancel—Remains in the configuration mode, without committing the configuration changes.
                             

                            Setting BGP Administrative Distance

                            Perform this task to specify the use of administrative distances that can be used to prefer one class of route over another.

                            SUMMARY STEPS

                              1.    configure

                              2.    router bgp as-number

                              3.    address-family { ipv4 | ipv6 } unicast

                              4.    distance bgp external-distance internal-distance local-distance

                              5.    Use the commit or end command.


                            DETAILED STEPS
                                Command or Action Purpose
                              Step 1 configure


                              Example:
                              RP/0/RSP0/CPU0:router# configure
                               

                              Enters global configuration mode.

                               
                              Step 2 router bgp as-number


                              Example:
                              RP/0/RSP0/CPU0:router(config)# router bgp 120
                               

                              Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                               
                              Step 3 address-family { ipv4 | ipv6 } unicast


                              Example:
                              RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                               

                              Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                              To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                               
                              Step 4 distance bgp external-distance internal-distance local-distance


                              Example:
                              RP/0/RSP0/CPU0:router(config-bgp-af)# distance bgp 20 20 200
                               

                              Sets the external, internal, and local administrative distances to prefer one class of routes over another. The higher the value, the lower the trust rating.

                               
                              Step 5 Use the commit or end command.  

                              commit—Saves the configuration changes, and remains within the configuration session.

                              end—Prompts user to take one of these actions:
                              • Yes— Saves configuration changes and exits the configuration session.
                              • No—Exits the configuration session without committing the configuration changes.
                              • Cancel—Remains in the configuration mode, without committing the configuration changes.
                               

                              Configuring a BGP Neighbor Group and Neighbors

                              Perform this task to configure BGP neighbor groups and apply the neighbor group configuration to a neighbor. A neighbor group is a template that holds address family-independent and address family-dependent configurations associated with the neighbor.

                              After a neighbor group is configured, each neighbor can inherit the configuration through the use command. If a neighbor is configured to use a neighbor group, the neighbor (by default) inherits the entire configuration of the neighbor group, which includes the address family-independent and address family-dependent configurations. The inherited configuration can be overridden if you directly configure commands for the neighbor or configure session groups or address family groups through the use command.

                              You can configure an address family-independent configuration under the neighbor group. An address family-dependent configuration requires you to configure the address family under the neighbor group to enter address family submode.

                              From neighbor group configuration mode, you can configure address family-independent parameters for the neighbor group. Use the address-family command when in the neighbor group configuration mode.

                              After specifying the neighbor group name using the neighbor group command, you can assign options to the neighbor group.


                              Note


                              All commands that can be configured under a specified neighbor group can be configured under a neighbor.


                              SUMMARY STEPS

                                1.    configure

                                2.    router bgp as-number

                                3.    address-family { ipv4 | ipv6 } unicast

                                4.    exit

                                5.    neighbor-group name

                                6.    remote-as as-number

                                7.    address-family { ipv4 | ipv6 } unicast

                                8.    route-policy route-policy-name { in | out }

                                9.    exit

                                10.    exit

                                11.    neighbor ip-address

                                12.    use neighbor-group group-name

                                13.    remote-as as-number

                                14.    Use the commit or end command.


                              DETAILED STEPS
                                  Command or Action Purpose
                                Step 1 configure


                                Example:
                                RP/0/RSP0/CPU0:router# configure
                                 

                                Enters global configuration mode.

                                 
                                Step 2 router bgp as-number


                                Example:
                                RP/0/RSP0/CPU0:router(config)# router bgp 120 
                                 

                                Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                 
                                Step 3 address-family { ipv4 | ipv6 } unicast


                                Example:
                                RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                 

                                Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                 
                                Step 4 exit


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-af)# exit
                                 

                                Exits the current configuration mode.

                                 
                                Step 5 neighbor-group name


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group nbr-grp-A
                                 

                                Places the router in neighbor group configuration mode.

                                 
                                Step 6 remote-as as-number


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# remote-as 2002
                                 

                                Creates a neighbor and assigns a remote autonomous system number to it.

                                 
                                Step 7 address-family { ipv4 | ipv6 } unicast


                                Example:
                                RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                 

                                Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                 
                                Step 8 route-policy route-policy-name { in | out }


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# route-policy drop-as-1234 in
                                 

                                (Optional) Applies the specified policy to inbound IPv4 unicast routes.

                                 
                                Step 9 exit


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)# exit
                                 

                                Exits the current configuration mode.

                                 
                                Step 10 exit


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
                                 

                                Exits the current configuration mode.

                                 
                                Step 11 neighbor ip-address


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                 

                                Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                 
                                Step 12 use neighbor-group group-name


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group nbr-grp-A
                                 

                                (Optional) Specifies that the BGP neighbor inherit configuration from the specified neighbor group.

                                 
                                Step 13 remote-as as-number


                                Example:
                                RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002
                                 

                                Creates a neighbor and assigns a remote autonomous system number to it.

                                 
                                Step 14 Use the commit or end command.  

                                commit—Saves the configuration changes, and remains within the configuration session.

                                end—Prompts user to take one of these actions:
                                • Yes— Saves configuration changes and exits the configuration session.
                                • No—Exits the configuration session without committing the configuration changes.
                                • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                 

                                Configuring a Route Reflector for BGP

                                Perform this task to configure a route reflector for BGP.

                                All the neighbors configured with the route-reflector-clientcommand are members of the client group, and the remaining iBGP peers are members of the nonclient group for the local route reflector.

                                Together, a route reflector and its clients form a cluster. A cluster of clients usually has a single route reflector. In such instances, the cluster is identified by the software as the router ID of the route reflector. To increase redundancy and avoid a single point of failure in the network, a cluster can have more than one route reflector. If it does, all route reflectors in the cluster must be configured with the same 4-byte cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster. The bgp cluster-id command is used to configure the cluster ID when the cluster has more than one route reflector.

                                SUMMARY STEPS

                                  1.    configure

                                  2.    router bgp as-number

                                  3.    bgp cluster-id cluster-id

                                  4.    neighbor ip-address

                                  5.    remote-as as-number

                                  6.    address-family { ipv4 | ipv6 } unicast

                                  7.    route-reflector-client

                                  8.    Use the commit or end command.


                                DETAILED STEPS
                                    Command or Action Purpose
                                  Step 1 configure


                                  Example:
                                  RP/0/RSP0/CPU0:router# configure
                                   

                                  Enters global configuration mode.

                                   
                                  Step 2 router bgp as-number


                                  Example:
                                  RP/0/RSP0/CPU0:router(config)# router bgp 120
                                   

                                  Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                   
                                  Step 3 bgp cluster-id cluster-id


                                  Example:
                                  RP/0/RSP0/CPU0:router(config-bgp)# bgp cluster-id 192.168.70.1
                                   

                                  Configures the local router as one of the route reflectors serving the cluster. It is configured with a specified cluster ID to identify the cluster.

                                   
                                  Step 4 neighbor ip-address


                                  Example:
                                    RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                    
                                   

                                  Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                   
                                  Step 5 remote-as as-number


                                  Example:
                                  RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2003
                                   

                                  Creates a neighbor and assigns a remote autonomous system number to it.

                                   
                                  Step 6 address-family { ipv4 | ipv6 } unicast


                                  Example:
                                  RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                   

                                  Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                  To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                   
                                  Step 7 route-reflector-client


                                  Example:
                                  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-reflector-client
                                   

                                  Configures the router as a BGP route reflector and configures the neighbor as its client.

                                   
                                  Step 8 Use the commit or end command.  

                                  commit—Saves the configuration changes, and remains within the configuration session.

                                  end—Prompts user to take one of these actions:
                                  • Yes— Saves configuration changes and exits the configuration session.
                                  • No—Exits the configuration session without committing the configuration changes.
                                  • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                   

                                  Configuring BGP Route Filtering by Route Policy

                                  Perform this task to configure BGP routing filtering by route policy.

                                  Before You Begin

                                  See the Implementing Routing Policy on Cisco ASR 9000 Series Router module of Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide (this publication) for a list of the supported attributes and operations that are valid for inbound and outbound neighbor policy filtering.

                                  SUMMARY STEPS

                                    1.    configure

                                    2.    route-policy name

                                    3.    end-policy

                                    4.    router bgp as-number

                                    5.    neighbor ip-address

                                    6.    address-family { ipv4 | ipv6 } unicast

                                    7.    route-policy route-policy-name { in | out }

                                    8.    Use the commit or end command.


                                  DETAILED STEPS
                                      Command or Action Purpose
                                    Step 1 configure


                                    Example:
                                    RP/0/RSP0/CPU0:router# configure
                                     

                                    Enters global configuration mode.

                                     
                                    Step 2 route-policy name


                                    Example:
                                    RP/0/RSP0/CPU0:router(config)# route-policy drop-as-1234
                                      RP/0/RSP0/CPU0:router(config-rpl)# if as-path passes-through '1234' then
                                      RP/0/RSP0/CPU0:router(config-rpl)# apply check-communities
                                      RP/0/RSP0/CPU0:router(config-rpl)# else
                                      RP/0/RSP0/CPU0:router(config-rpl)# pass
                                      RP/0/RSP0/CPU0:router(config-rpl)# endif
                                      
                                     

                                    (Optional) Creates a route policy and enters route policy configuration mode, where you can define the route policy.

                                     
                                    Step 3 end-policy


                                    Example:
                                    RP/0/RSP0/CPU0:router(config-rpl)# end-policy
                                     

                                    (Optional) Ends the definition of a route policy and exits route policy configuration mode.

                                     
                                    Step 4 router bgp as-number


                                    Example:
                                    RP/0/RSP0/CPU0:router(config)# router bgp 120
                                     

                                    Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                     
                                    Step 5 neighbor ip-address


                                    Example:
                                    RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                     

                                    Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                     
                                    Step 6 address-family { ipv4 | ipv6 } unicast


                                    Example:
                                    RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                     

                                    Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                    To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                     
                                    Step 7 route-policy route-policy-name { in | out }


                                    Example:
                                    RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy drop-as-1234 in
                                     

                                    Applies the specified policy to inbound routes.

                                     
                                    Step 8 Use the commit or end command.  

                                    commit—Saves the configuration changes, and remains within the configuration session.

                                    end—Prompts user to take one of these actions:
                                    • Yes— Saves configuration changes and exits the configuration session.
                                    • No—Exits the configuration session without committing the configuration changes.
                                    • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                     

                                    Configuring BGP Next-Hop Trigger Delay

                                    Perform this task to configure BGP next-hop trigger delay. The Routing Information Base (RIB) classifies the dampening notifications based on the severity of the changes. Event notifications are classified as critical and noncritical. This task allows you to specify the minimum batching interval for the critical and noncritical events.

                                    SUMMARY STEPS

                                      1.    configure

                                      2.    router bgp as-number

                                      3.    address-family { ipv4 | ipv6 } unicast

                                      4.    nexthop trigger-delay { critical delay | non-critical delay }

                                      5.    Use the commit or end command.


                                    DETAILED STEPS
                                        Command or Action Purpose
                                      Step 1 configure


                                      Example:
                                      RP/0/RSP0/CPU0:router# configure
                                       

                                      Enters global configuration mode.

                                       
                                      Step 2 router bgp as-number


                                      Example:
                                      RP/0/RSP0/CPU0:router(config)# router bgp 120
                                       

                                      Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                       
                                      Step 3 address-family { ipv4 | ipv6 } unicast


                                      Example:
                                      RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                       

                                      Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                      To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                       
                                      Step 4 nexthop trigger-delay { critical delay | non-critical delay }


                                      Example:
                                      RP/0/RSP0/CPU0:router(config-bgp-af)# nexthop trigger-delay critical 15000
                                       

                                      Sets the critical next-hop trigger delay.

                                       
                                      Step 5 Use the commit or end command.  

                                      commit—Saves the configuration changes, and remains within the configuration session.

                                      end—Prompts user to take one of these actions:
                                      • Yes— Saves configuration changes and exits the configuration session.
                                      • No—Exits the configuration session without committing the configuration changes.
                                      • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                       

                                      Disabling Next-Hop Processing on BGP Updates

                                      Perform this task to disable next-hop calculation for a neighbor and insert your own address in the next-hop field of BGP updates. Disabling the calculation of the best next hop to use when advertising a route causes all routes to be advertised with the network device as the next hop.


                                      Note


                                      Next-hop processing can be disabled for address family group, neighbor group, or neighbor address family.


                                      SUMMARY STEPS

                                        1.    configure

                                        2.    router bgp as-number

                                        3.    neighbor ip-address

                                        4.    remote-as as-number

                                        5.    address-family { ipv4 | ipv6 } unicast

                                        6.    next-hop-self

                                        7.    Use the commit or end command.


                                      DETAILED STEPS
                                          Command or Action Purpose
                                        Step 1 configure


                                        Example:
                                        RP/0/RSP0/CPU0:router# configure
                                         

                                        Enters global configuration mode.

                                         
                                        Step 2 router bgp as-number


                                        Example:
                                        RP/0/RSP0/CPU0:router(config)# router bgp 120
                                         

                                        Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                         
                                        Step 3 neighbor ip-address


                                        Example:
                                        RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                         

                                        Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                         
                                        Step 4 remote-as as-number


                                        Example:
                                        RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 206
                                         

                                        Creates a neighbor and assigns a remote autonomous system number to it.

                                         
                                        Step 5 address-family { ipv4 | ipv6 } unicast


                                        Example:
                                        RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                         

                                        Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                        To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                         
                                        Step 6 next-hop-self


                                        Example:
                                        RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# next-hop-self
                                         

                                        Sets the next-hop attribute for all routes advertised to the specified neighbor to the address of the local router. Disabling the calculation of the best next hop to use when advertising a route causes all routes to be advertised with the local network device as the next hop.

                                         
                                        Step 7 Use the commit or end command.  

                                        commit—Saves the configuration changes, and remains within the configuration session.

                                        end—Prompts user to take one of these actions:
                                        • Yes— Saves configuration changes and exits the configuration session.
                                        • No—Exits the configuration session without committing the configuration changes.
                                        • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                         

                                        Configuring BGP Community and Extended-Community Advertisements

                                        Perform this task to specify that community/extended-community attributes should be sent to an eBGP neighbor. These attributes are not sent to an eBGP neighbor by default. By contrast, they are always sent to iBGP neighbors. This section provides examples on how to enable sending community attributes. The send-community-ebgp keyword can be replaced by the send-extended-community-ebgp keyword to enable sending extended-communities.

                                        If the send-community-ebgp command is configured for a neighbor group or address family group, all neighbors using the group inherit the configuration. Configuring the command specifically for a neighbor overrides inherited values.


                                        Note


                                        BGP community and extended-community filtering cannot be configured for iBGP neighbors. Communities and extended-communities are always sent to iBGP neighbors under IPv4, IPv6, VPNv4, and MDT address families.


                                        SUMMARY STEPS

                                          1.    configure

                                          2.    router bgp as-number

                                          3.    neighbor ip-address

                                          4.    remote-as as-number

                                          5.    address-family{ipv4{labeled-unicast | mdt | multicast | mvpn | tunnel | unicast} | ipv6 {labeled-unicast | mvpn | unicast}}

                                          6.    Use one of these commands:

                                          • send-community-ebgp
                                          • send-extended-community-ebgp

                                          7.    Use the commit or end command.


                                        DETAILED STEPS
                                            Command or Action Purpose
                                          Step 1 configure


                                          Example:
                                          RP/0/RSP0/CPU0:router# configure
                                           

                                          Enters global configuration mode.

                                           
                                          Step 2 router bgp as-number


                                          Example:
                                          RP/0/RSP0/CPU0:router(config)# router bgp 120
                                           

                                          Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                           
                                          Step 3 neighbor ip-address


                                          Example:
                                          RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                           

                                          Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                           
                                          Step 4 remote-as as-number


                                          Example:
                                          RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002 
                                           

                                          Creates a neighbor and assigns a remote autonomous system number to it.

                                           
                                          Step 5 address-family{ipv4{labeled-unicast | mdt | multicast | mvpn | tunnel | unicast} | ipv6 {labeled-unicast | mvpn | unicast}}


                                          Example:
                                          RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv6 unicast
                                           

                                          Enters neighbor address family configuration mode for the specified address family. Use either ipv4 or ipv6 address family keyword with one of the specified address family sub mode identifiers.

                                          IPv6 address family mode supports these sub modes:
                                          • labeled-unicast
                                          • mvpn
                                          • unicast
                                          IPv4 address family mode supports these sub modes:
                                          • labeled-unicast
                                          • mdt
                                          • multicast
                                          • mvpn
                                          • tunnel
                                          • unicast

                                          Refer the address-family (BGP) command in BGP Commands module of Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference for more information on the Address Family Submode support.

                                           
                                          Step 6 Use one of these commands:
                                          • send-community-ebgp
                                          • send-extended-community-ebgp


                                          Example:
                                          RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# send-community-ebgp

                                          or

                                          RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# send-extended-community-ebgp
                                           

                                          Specifies that the router send community attributes or extended community attributes (which are disabled by default for eBGP neighbors) to a specified eBGP neighbor.

                                           
                                          Step 7 Use the commit or end command.  

                                          commit—Saves the configuration changes, and remains within the configuration session.

                                          end—Prompts user to take one of these actions:
                                          • Yes— Saves configuration changes and exits the configuration session.
                                          • No—Exits the configuration session without committing the configuration changes.
                                          • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                           

                                          Configuring the BGP Cost Community

                                          Perform this task to configure the BGP cost community.

                                          BGP receives multiple paths to the same destination and it uses the best-path algorithm to decide which is the best path to install in RIB. To enable users to determine an exit point after partial comparison, the cost community is defined to tie-break equal paths during the best-path selection process.

                                          SUMMARY STEPS

                                            1.    configure

                                            2.    route-policy name

                                            3.    set extcommunity cost { cost-extcommunity-set-name | cost-inline-extcommunity-set } [ additive ]

                                            4.    end-policy

                                            5.    router bgp as-number

                                            6.    Do one of the following:

                                            • default-information originate
                                            • aggregate-address address/mask-length [ as-set ] [ as-confed-set ] [ summary-only ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute connected [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute eigrp process-id [ match { external | internal }] [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute isis process-id [ level { 1 | 1-inter-area | 2 }] [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute ospf process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]

                                            7.    Do one of the following:

                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv4 mdt | ipv6 unicast | ipv6 multicast | vpnv4 unicast | vpnv6 unicast } redistribute ospfv3 process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute rip [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute static [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } network { ip-address/prefix-length | ip-address mask } [ route-policy route-policy-name ]
                                            • neighbor ip-address remote-as as-number address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv4 ipv6 unicast | vpnv4 unicast }
                                            • route-policy route-policy-name { in | out }

                                            8.    Use the commit or end command.

                                            9.    show bgp [ vrf vrf-name ] ip-address


                                          DETAILED STEPS
                                              Command or Action Purpose
                                            Step 1 configure


                                            Example:
                                            RP/0/RSP0/CPU0:router# configure
                                             

                                            Enters global configuration mode.

                                             
                                            Step 2 route-policy name


                                            Example:
                                            RP/0/RSP0/CPU0:router(config)# route-policy costA
                                             

                                            Enters route policy configuration mode and specifies the name of the route policy to be configured.

                                             
                                            Step 3 set extcommunity cost { cost-extcommunity-set-name | cost-inline-extcommunity-set } [ additive ]


                                            Example:
                                            RP/0/RSP0/CPU0:router(config)# set extcommunity cost cost_A
                                             

                                            Specifies the BGP extended community attribute for cost.

                                             
                                            Step 4 end-policy


                                            Example:
                                            RP/0/RSP0/CPU0:router(config)# end-policy
                                             

                                            Ends the definition of a route policy and exits route policy configuration mode.

                                             
                                            Step 5 router bgp as-number


                                            Example:
                                            RP/0/RSP0/CPU0:router(config)# router bgp 120
                                             

                                            Enters BGP configuration mode allowing you to configure the BGP routing process.

                                             
                                            Step 6 Do one of the following:
                                            • default-information originate
                                            • aggregate-address address/mask-length [ as-set ] [ as-confed-set ] [ summary-only ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute connected [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute eigrp process-id [ match { external | internal }] [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute isis process-id [ level { 1 | 1-inter-area | 2 }] [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute ospf process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                             

                                            Applies the cost community to the attach point (route policy).

                                             
                                            Step 7 Do one of the following:
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv4 mdt | ipv6 unicast | ipv6 multicast | vpnv4 unicast | vpnv6 unicast } redistribute ospfv3 process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute rip [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } redistribute static [ metric metric-value ] [ route-policy route-policy-name ]
                                            • address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv6 unicast | vpnv4 unicast } network { ip-address/prefix-length | ip-address mask } [ route-policy route-policy-name ]
                                            • neighbor ip-address remote-as as-number address-family { ipv4 unicast | ipv4 multicast | ipv4 tunnel | ipv4 ipv6 unicast | vpnv4 unicast }
                                            • route-policy route-policy-name { in | out }
                                             
                                             
                                            Step 8 Use the commit or end command.  

                                            commit—Saves the configuration changes, and remains within the configuration session.

                                            end—Prompts user to take one of these actions:
                                            • Yes— Saves configuration changes and exits the configuration session.
                                            • No—Exits the configuration session without committing the configuration changes.
                                            • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                             
                                            Step 9 show bgp [ vrf vrf-name ] ip-address


                                            Example:
                                            RP/0/RSP0/CPU0:router# show bgp 172.168.40.24
                                             

                                            Displays the cost community in the following format:

                                            Cost: POI : cost-community-ID : cost-number

                                             

                                            Configuring Software to Store Updates from a Neighbor

                                            Perform this task to configure the software to store updates received from a neighbor.

                                            The soft-reconfiguration inbound command causes a route refresh request to be sent to the neighbor if the neighbor is route refresh capable. If the neighbor is not route refresh capable, the neighbor must be reset to relearn received routes using the clear bgp soft command. See the Resetting Neighbors Using BGP Inbound Soft Reset.


                                            Note


                                            Storing updates from a neighbor works only if either the neighbor is route refresh capable or the soft-reconfiguration inbound command is configured. Even if the neighbor is route refresh capable and the soft-reconfiguration inbound command is configured, the original routes are not stored unless the always option is used with the command. The original routes can be easily retrieved with a route refresh request. Route refresh sends a request to the peer to resend its routing information. The soft-reconfiguration inbound command stores all paths received from the peer in an unmodified form and refers to these stored paths during the clear. Soft reconfiguration is memory intensive.


                                            SUMMARY STEPS

                                              1.    configure

                                              2.    router bgp as-number

                                              3.    neighbor ip-address

                                              4.    address-family { ipv4 | ipv6 } unicast

                                              5.    soft-reconfiguration inbound [ always]

                                              6.    Use the commit or end command.


                                            DETAILED STEPS
                                                Command or Action Purpose
                                              Step 1 configure


                                              Example:
                                              RP/0/RSP0/CPU0:router# configure
                                               

                                              Enters global configuration mode.

                                               
                                              Step 2 router bgp as-number


                                              Example:
                                              RP/0/RSP0/CPU0:router(config)# router bgp 120 
                                               

                                              Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                               
                                              Step 3 neighbor ip-address


                                              Example:
                                              RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                               

                                              Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                               
                                              Step 4 address-family { ipv4 | ipv6 } unicast


                                              Example:
                                              RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                               

                                              Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                              To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                               
                                              Step 5 soft-reconfiguration inbound [ always]


                                              Example:
                                              RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# soft-reconfiguration inbound always
                                               

                                              Configures the software to store updates received from a specified neighbor. Soft reconfiguration inbound causes the software to store the original unmodified route in addition to a route that is modified or filtered. This allows a “soft clear” to be performed after the inbound policy is changed.

                                              Soft reconfiguration enables the software to store the incoming updates before apply policy if route refresh is not supported by the peer (otherwise a copy of the update is not stored). The always keyword forces the software to store a copy even when route refresh is supported by the peer.

                                               
                                              Step 6 Use the commit or end command.  

                                              commit—Saves the configuration changes, and remains within the configuration session.

                                              end—Prompts user to take one of these actions:
                                              • Yes— Saves configuration changes and exits the configuration session.
                                              • No—Exits the configuration session without committing the configuration changes.
                                              • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                               

                                              Configuring a VPN Routing and Forwarding Instance in BGP

                                              Layer 2 and Layer 3 (virtual private network) VPN can be configured only if there is an available Layer 3 VPN license for the line card slot on which the feature is being configured.

                                              If the advanced IP license is enabled, 4096 Layer 3 VPN routing and forwarding instances (VRFs) can be configured on an interface. If the infrastructure VRF license is enabled, eight Layer 3 VRFs can be configured on the line card. See the Software Entitlement on Cisco ASR 9000 Series Router module in Cisco ASR 9000 Series Aggregation Services Router System Management Configuration Guide for more information on advanced IP licencing.

                                              The following error message appears if the appropriate licence is not enabled:
                                              RP/0/RSP0/CPU0:router#LC/0/0/CPU0:Dec 15 17:57:53.653 : rsi_agent[247]:
                                              %LICENSE-ASR9K_LICENSE-2-INFRA_VRF_NEEDED : 5 VRF(s) are configured without license A9K-iVRF-LIC in violation of the Software Right To Use Agreement. 
                                              This feature may be disabled by the system without the appropriate license.
                                              Contact Cisco to purchase the license immediately to avoid potential service interruption.

                                              The following tasks are used to configure a VPN routing and forwarding (VRF) instance in BGP:

                                              Defining Virtual Routing and Forwarding Tables in Provider Edge Routers

                                              Perform this task to define the VPN routing and forwarding (VRF) tables in the provider edge (PE) routers.

                                              SUMMARY STEPS

                                                1.    configure

                                                2.    vrf vrf-name

                                                3.    address-family { ipv4 | ipv6 } unicast

                                                4.    maximum prefix maximum [ threshold ]

                                                5.    import route-policy policy-name

                                                6.    import route-target [ as-number : nn | ip-address : nn ]

                                                7.    export route-policy policy-name

                                                8.    export route-target [ as-number : nn | ip-address : nn ]

                                                9.    Use the commit or end command.


                                              DETAILED STEPS
                                                  Command or Action Purpose
                                                Step 1 configure


                                                Example:
                                                RP/0/RSP0/CPU0:router# configure
                                                 

                                                Enters global configuration mode.

                                                 
                                                Step 2 vrf vrf-name


                                                Example:
                                                RP/0/RSP0/CPU0:router(config)# vrf vrf_pe
                                                 

                                                Configures a VRF instance.

                                                 
                                                Step 3 address-family { ipv4 | ipv6 } unicast


                                                Example:
                                                RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                                 

                                                Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                                                To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                                 
                                                Step 4 maximum prefix maximum [ threshold ]


                                                Example:
                                                RP/0/RSP0/CPU0:router(config-vrf-af)# maximum prefix 2300
                                                 

                                                Configures a limit to the number of prefixes allowed in a VRF table.

                                                A maximum number of routes is applicable to dynamic routing protocols as well as static or connected routes.

                                                You can specify a threshold percentage of the prefix limit using the mid-threshold argument.

                                                 
                                                Step 5 import route-policy policy-name


                                                Example:
                                                RP/0/RSP0/CPU0:router(config-vrf-af)# import route-policy policy_a
                                                 

                                                (Optional) Provides finer control over what gets imported into a VRF. This import filter discards prefixes that do not match the specified policy-name argument.

                                                 
                                                Step 6 import route-target [ as-number : nn | ip-address : nn ]


                                                Example:
                                                RP/0/RSP0/CPU0:router(config-vrf-af)# import route-target 234:222
                                                 

                                                Specifies a list of route target (RT) extended communities. Only prefixes that are associated with the specified import route target extended communities are imported into the VRF.

                                                 
                                                Step 7 export route-policy policy-name


                                                Example:
                                                RP/0/RSP0/CPU0:router(config-vrf-af)# export route-policy policy_b
                                                 

                                                (Optional) Provides finer control over what gets exported into a VRF. This export filter discards prefixes that do not match the specified policy-name argument.

                                                 
                                                Step 8 export route-target [ as-number : nn | ip-address : nn ]


                                                Example:
                                                RP/0/RSP0/CPU0:routerr(config-vrf-af)# export route-target 123;234
                                                 

                                                Specifies a list of route target extended communities. Export route target communities are associated with prefixes when they are advertised to remote PEs. The remote PEs import them into VRFs which have import RTs that match these exported route target communities.

                                                 
                                                Step 9 Use the commit or end command.  

                                                commit—Saves the configuration changes, and remains within the configuration session.

                                                end—Prompts user to take one of these actions:
                                                • Yes— Saves configuration changes and exits the configuration session.
                                                • No—Exits the configuration session without committing the configuration changes.
                                                • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                 

                                                Configuring the Route Distinguisher

                                                The route distinguisher (RD) makes prefixes unique across multiple VPN routing and forwarding (VRF) instances.

                                                In the L3VPN multipath same route distinguisher (RD)environment, the determination of whether to install a prefix in RIB or not is based on the prefix's bestpath. In a rare misconfiguration situation, where the best pah is not a valid path to be installed in RIB, BGP drops the prefix and does not consider the other paths. The behavior is different for different RD setup, where the non-best multipath will be installed if the best multipath is invalid to be installed in RIB.

                                                Perform this task to configure the RD.

                                                SUMMARY STEPS

                                                  1.    configure

                                                  2.    router bgp as-number

                                                  3.    bgp router-id ip-address

                                                  4.    vrf vrf-name

                                                  5.    rd { as-number : nn | ip-address : nn | auto }

                                                  6.    Do one of the following:

                                                  • end
                                                  • commit


                                                DETAILED STEPS
                                                    Command or Action Purpose
                                                  Step 1 configure


                                                  Example:
                                                  RP/0/RSP0/CPU0:router# configure
                                                   

                                                  Enters global configuration mode.

                                                   
                                                  Step 2 router bgp as-number


                                                  Example:
                                                  RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                   

                                                  Enters BGP configuration mode allowing you to configure the BGP routing process.

                                                   
                                                  Step 3 bgp router-id ip-address


                                                  Example:
                                                  RP/0/RSP0/CPU0:router(config-bgp)# bgp router-id 10.0.0.0
                                                   

                                                  Configures a fixed router ID for the BGP-speaking router.

                                                   
                                                  Step 4 vrf vrf-name


                                                  Example:
                                                  RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_pe
                                                   

                                                  Configures a VRF instance.

                                                   
                                                  Step 5 rd { as-number : nn | ip-address : nn | auto }


                                                  Example:
                                                  RP/0/RSP0/CPU0:router(config-bgp-vrf)# rd 345:567
                                                   

                                                  Configures the route distinguisher.

                                                  Use the auto keyword if you want the router to automatically assign a unique RD to the VRF.

                                                  Automatic assignment of RDs is possible only if a router ID is configured using the bgp router-id command in router configuration mode. This allows you to configure a globally unique router ID that can be used for automatic RD generation. The router ID for the VRF does not need to be globally unique, and using the VRF router ID would be incorrect for automatic RD generation. Having a single router ID also helps in checkpointing RD information for BGP graceful restart, because it is expected to be stable across reboots.

                                                   
                                                  Step 6 Do one of the following:
                                                  • end
                                                  • commit


                                                  Example:
                                                  RP/0/RSP0/CPU0:router(config-bgp-vrf)# end

                                                  or

                                                  RP/0/RSP0/CPU0:router(config-bgp-vrf)# commit
                                                   

                                                  Saves configuration changes.

                                                  • When you issue the end command, the system prompts you to commit changes:
                                                      Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:
                                                    
                                                    • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC configuration mode.
                                                    • Entering no exits the configuration session and returns the router to EXEC configuration mode without committing the configuration changes.
                                                    • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
                                                  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
                                                   

                                                  Configuring PE-PE or PE-RR Interior BGP Sessions

                                                  To enable BGP to carry VPN reachability information between provider edge (PE) routers you must configure the PE-PE interior BGP (iBGP) sessions. A PE uses VPN information carried from the remote PE router to determine VPN connectivity and the label value to be used so the remote (egress) router can demultiplex the packet to the correct VPN during packet forwarding.

                                                  The PE-PE, PE-route reflector (RR) iBGP sessions are defined to all PE and RR routers that participate in the VPNs configured in the PE router.

                                                  Perform this task to configure PE-PE iBGP sessions and to configure global VPN options on a PE.

                                                  SUMMARY STEPS

                                                    1.    configure

                                                    2.    router bgp as-number

                                                    3.    address-family vpnv4 unicast

                                                    4.    exit

                                                    5.    neighbor ip-address

                                                    6.    remote-as as-number

                                                    7.    description text

                                                    8.    password { clear | encrypted } password

                                                    9.    shutdown

                                                    10.    timers keepalive hold-time

                                                    11.    update-source type interface-id

                                                    12.    address-family vpnv4 unicast

                                                    13.    route-policy route-policy-name in

                                                    14.    route-policy route-policy-name out

                                                    15.    Use the commit or end command.


                                                  DETAILED STEPS
                                                      Command or Action Purpose
                                                    Step 1 configure


                                                    Example:
                                                    RP/0/RSP0/CPU0:router# configure
                                                     

                                                    Enters global configuration mode.

                                                     
                                                    Step 2 router bgp as-number


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                     

                                                    Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                     
                                                    Step 3 address-family vpnv4 unicast


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp)# address-family vpvn4 unicast
                                                     

                                                    Enters VPN address family configuration mode.

                                                     
                                                    Step 4 exit


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-af)# exit
                                                     

                                                    Exits the current configuration mode.

                                                     
                                                    Step 5 neighbor ip-address


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.16.1.1
                                                     

                                                    Configures a PE iBGP neighbor.

                                                     
                                                    Step 6 remote-as as-number


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
                                                     

                                                    Assigns the neighbor a remote autonomous system number.

                                                     
                                                    Step 7 description text


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# description neighbor 172.16.1.1
                                                     

                                                    (Optional) Provides a description of the neighbor. The description is used to save comments and does not affect software function.

                                                     
                                                    Step 8 password { clear | encrypted } password


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# password encrypted 123abc
                                                     

                                                    Enables Message Digest 5 (MD5) authentication on the TCP connection between the two BGP neighbors.

                                                     
                                                    Step 9 shutdown


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# shutdown
                                                     

                                                    Terminates any active sessions for the specified neighbor and removes all associated routing information.

                                                     
                                                    Step 10 timers keepalive hold-time


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# timers 12000 200
                                                     

                                                    Set the timers for the BGP neighbor.

                                                     
                                                    Step 11 update-source type interface-id


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# update-source gigabitEthernet 0/1/5/0
                                                     

                                                    Allows iBGP sessions to use the primary IP address from a specific interface as the local address when forming an iBGP session with a neighbor.

                                                     
                                                    Step 12 address-family vpnv4 unicast


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family vpvn4 unicast
                                                     

                                                    Enters VPN neighbor address family configuration mode.

                                                     
                                                    Step 13 route-policy route-policy-name in


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy pe-pe-vpn-in in
                                                     

                                                    Specifies a routing policy for an inbound route. The policy can be used to filter routes or modify route attributes.

                                                     
                                                    Step 14 route-policy route-policy-name out


                                                    Example:
                                                    RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy pe-pe-vpn-out out
                                                     

                                                    Specifies a routing policy for an outbound route. The policy can be used to filter routes or modify route attributes.

                                                     
                                                    Step 15 Use the commit or end command.  

                                                    commit—Saves the configuration changes, and remains within the configuration session.

                                                    end—Prompts user to take one of these actions:
                                                    • Yes— Saves configuration changes and exits the configuration session.
                                                    • No—Exits the configuration session without committing the configuration changes.
                                                    • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                     

                                                    Configuring Route Reflector to Hold Routes That Have a Defined Set of RT Communities

                                                    A provider edge (PE) needs to hold the routes that match the import route targets (RTs) of the VPNs configured on it. The PE router can discard all other VPNv4 routes. But, a route reflector (RR) must retain all VPNv4 routes, because it might peer with PE routers and different PEs might require different RT-tagged VPNv4 (making RRs non-scalable). You can configure an RR to only hold routes that have a defined set of RT communities. Also, a number of the RRs can be configured to service a different set of VPNs (thereby achieving some scalability). A PE is then made to peer with all RRs that service the VRFs configured on the PE. When a new VRF is configured with an RT for which the PE does not already hold routes, the PE issues route refreshes to the RRs and retrieves the relevant VPN routes.


                                                    Note


                                                    Note that this process can be more efficient if the PE-RR session supports extended community outbound route filter (ORF).


                                                    Perform this task to configure a reflector to retain routes tagged with specific RTs.

                                                    SUMMARY STEPS

                                                      1.    configure

                                                      2.    router bgp as-number

                                                      3.    address-family vpnv4 unicast

                                                      4.    retain route-target { all | route-policy route-policy-name }

                                                      5.    Use the commit or end command.


                                                    DETAILED STEPS
                                                        Command or Action Purpose
                                                      Step 1 configure


                                                      Example:
                                                      RP/0/RSP0/CPU0:router# configure
                                                       

                                                      Enters global configuration mode.

                                                       
                                                      Step 2 router bgp as-number


                                                      Example:
                                                      RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                       

                                                      Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                       
                                                      Step 3 address-family vpnv4 unicast


                                                      Example:
                                                      RP/0/RSP0/CPU0:router(config-bgp)# address-family vpvn4 unicast
                                                       

                                                      Enters VPN address family configuration mode.

                                                       
                                                      Step 4 retain route-target { all | route-policy route-policy-name }


                                                      Example:
                                                      RP/0/RSP0/CPU0:router(config-bgp-af)# retain route-target route-policy rr_ext-comm
                                                       

                                                      Configures a reflector to retain routes tagged with particular RTs. Use the route-policy-name argument for the policy name that lists the extended communities that a path should have in order for the RR to retain that path.

                                                      Note   

                                                      The all keyword is not required, because this is the default behavior of a route reflector.

                                                       
                                                      Step 5 Use the commit or end command.  

                                                      commit—Saves the configuration changes, and remains within the configuration session.

                                                      end—Prompts user to take one of these actions:
                                                      • Yes— Saves configuration changes and exits the configuration session.
                                                      • No—Exits the configuration session without committing the configuration changes.
                                                      • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                       

                                                      Configuring BGP as a PE-CE Protocol

                                                      Perform this task to configure BGP on the PE and establish PE-CE communication using BGP.

                                                      SUMMARY STEPS

                                                        1.    configure

                                                        2.    router bgp as-number

                                                        3.    vrf vrf-name

                                                        4.    bgp router-id ip-address

                                                        5.    label-allocation-mode per-ce

                                                        6.    address-family { ipv4 | ipv6 } unicast

                                                        7.    network { ip-address / prefix-length | ip-address mask }

                                                        8.    aggregate-address address / mask-length

                                                        9.    exit

                                                        10.    neighbor ip-address

                                                        11.    remote-as as-number

                                                        12.    password { clear | encrypted } password

                                                        13.    ebgp-multihop [ ttl-value ]

                                                        14.    Do one of the following:

                                                        • address-family { ipv4 | ipv6 } unicast
                                                        • address-family {ipv4 {unicast | labeled-unicast} | ipv6 unicast}

                                                        15.    site-of-origin [ as-number : nn | ip-address : nn ]

                                                        16.    as-override

                                                        17.    allowas-in [ as-occurrence-number ]

                                                        18.    route-policy route-policy-name in

                                                        19.    route-policy route-policy-name out

                                                        20.    Use the commit or end command.


                                                      DETAILED STEPS
                                                          Command or Action Purpose
                                                        Step 1 configure


                                                        Example:
                                                        RP/0/RSP0/CPU0:router# configure
                                                         

                                                        Enters global configuration mode.

                                                         
                                                        Step 2 router bgp as-number


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                         

                                                        Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                         
                                                        Step 3 vrf vrf-name


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_pe_2
                                                         

                                                        Enables BGP routing for a particular VRF on the PE router.

                                                         
                                                        Step 4 bgp router-id ip-address


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf)# bgp router-id 172.16.9.9
                                                         

                                                        Configures a fixed router ID for a BGP-speaking router.

                                                         
                                                        Step 5 label-allocation-mode per-ce


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf)# label-allocation-mode per-ce
                                                         
                                                        • Configures the per-CE label allocation mode to avoid an extra lookup on the PE router and conserve label space (per-prefix is the default label allocation mode). In this mode, the PE router allocates one label for every immediate next-hop (in most cases, this would be a CE router). This label is directly mapped to the next hop, so there is no VRF route lookup performed during data forwarding. However, the number of labels allocated would be one for each CE rather than one for each VRF. Because BGP knows all the next hops, it assigns a label for each next hop (not for each PE-CE interface). When the outgoing interface is a multiaccess interface and the media access control (MAC) address of the neighbor is not known, Address Resolution Protocol (ARP) is triggered during packet forwarding.
                                                        • The per-vrf keyword configures the same label to be used for all the routes advertised from a unique VRF.
                                                         
                                                        Step 6 address-family { ipv4 | ipv6 } unicast


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                                         

                                                        Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                                        To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                                         
                                                        Step 7 network { ip-address / prefix-length | ip-address mask }


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# network 172.16.5.5/24
                                                                       
                                                         

                                                        Originates a network prefix in the address family table in the VRF context.

                                                         
                                                        Step 8 aggregate-address address / mask-length


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# aggregate-address 10.0.0.0/24
                                                         

                                                        Configures aggregation in the VRF address family context to summarize routing information to reduce the state maintained in the core. This summarization introduces some inefficiency in the PE edge, because an additional lookup is required to determine the ultimate next hop for a packet. When configured, a summary prefix is advertised instead of a set of component prefixes, which are more specifics of the aggregate. The PE advertises only one label for the aggregate. Because component prefixes could have different next hops to CEs, an additional lookup has to be performed during data forwarding.

                                                         
                                                        Step 9 exit


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# exit
                                                         

                                                        Exits the current configuration mode.

                                                         
                                                        Step 10 neighbor ip-address


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 10.0.0.0
                                                         

                                                        Configures a CE neighbor. The ip-address argument must be a private address.

                                                         
                                                        Step 11 remote-as as-number


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# remote-as 2
                                                         

                                                        Configures the remote AS for the CE neighbor.

                                                         
                                                        Step 12 password { clear | encrypted } password


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# password encrypted 234xyz
                                                         

                                                        Enable Message Digest 5 (MD5) authentication on a TCP connection between two BGP neighbors.

                                                         
                                                        Step 13 ebgp-multihop [ ttl-value ]


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# ebgp-multihop 55
                                                         

                                                        Configures the CE neighbor to accept and attempt BGP connections to external peers residing on networks that are not directly connected.

                                                         
                                                        Step 14 Do one of the following:
                                                        • address-family { ipv4 | ipv6 } unicast
                                                        • address-family {ipv4 {unicast | labeled-unicast} | ipv6 unicast}


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                                         

                                                        Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                                        To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                                         
                                                        Step 15 site-of-origin [ as-number : nn | ip-address : nn ]


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# site-of-origin 234:111
                                                         

                                                        Configures the site-of-origin (SoO) extended community. Routes that are learned from this CE neighbor are tagged with the SoO extended community before being advertised to the rest of the PEs. SoO is frequently used to detect loops when as-override is configured on the PE router. If the prefix is looped back to the same site, the PE detects this and does not send the update to the CE.

                                                         
                                                        Step 16 as-override


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# as-override
                                                         

                                                        Configures AS override on the PE router. This causes the PE router to replace the CE’s ASN with its own (PE) ASN.

                                                        Note   

                                                        This loss of information could lead to routing loops; to avoid loops caused by as-override, use it in conjunction with site-of-origin.

                                                         
                                                        Step 17 allowas-in [ as-occurrence-number ]


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# allowas-in 5
                                                         

                                                        Allows an AS path with the PE autonomous system number (ASN) a specified number of times.

                                                        Hub and spoke VPN networks need the looping back of routing information to the HUB PE through the HUB CE. When this happens, due to the presence of the PE ASN, the looped-back information is dropped by the HUB PE. To avoid this, use the allowas-in command to allow prefixes even if they have the PEs ASN up to the specified number of times.

                                                         
                                                        Step 18 route-policy route-policy-name in


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# route-policy pe_ce_in_policy in
                                                         

                                                        Specifies a routing policy for an inbound route. The policy can be used to filter routes or modify route attributes.

                                                         
                                                        Step 19 route-policy route-policy-name out


                                                        Example:
                                                        RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# route-policy pe_ce_out_policy out
                                                         

                                                        Specifies a routing policy for an outbound route. The policy can be used to filter routes or modify route attributes.

                                                         
                                                        Step 20 Use the commit or end command.  

                                                        commit—Saves the configuration changes, and remains within the configuration session.

                                                        end—Prompts user to take one of these actions:
                                                        • Yes— Saves configuration changes and exits the configuration session.
                                                        • No—Exits the configuration session without committing the configuration changes.
                                                        • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                         

                                                        Redistribution of IGPs to BGP

                                                        Perform this task to configure redistribution of a protocol into the VRF address family.

                                                        Even if Interior Gateway Protocols (IGPs) are used as the PE-CE protocol, the import logic happens through BGP. Therefore, all IGP routes have to be imported into the BGP VRF table.

                                                        SUMMARY STEPS

                                                          1.    configure

                                                          2.    router bgp as-number

                                                          3.    vrf vrf-name

                                                          4.    address-family { ipv4 | ipv6 } unicast

                                                          5.    Do one of the following:

                                                          • redistribute connected [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute eigrp process-id [ match { external | internal }] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute isis process-id [ level { 1 | 1-inter-area | 2 }] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute ospf process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute ospfv3 process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute rip [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute static [ metric metric-value ] [ route-policy route-policy-name ]

                                                          6.    Use the commit or end command.


                                                        DETAILED STEPS
                                                            Command or Action Purpose
                                                          Step 1 configure


                                                          Example:
                                                          RP/0/RSP0/CPU0:router# configure
                                                           

                                                          Enters global configuration mode.

                                                           
                                                          Step 2 router bgp as-number


                                                          Example:
                                                          RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                           

                                                          Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                           
                                                          Step 3 vrf vrf-name


                                                          Example:
                                                          RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_a
                                                           

                                                          Enables BGP routing for a particular VRF on the PE router.

                                                           
                                                          Step 4 address-family { ipv4 | ipv6 } unicast


                                                          Example:
                                                          RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                                           

                                                          Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                                          To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                                           
                                                          Step 5 Do one of the following:
                                                          • redistribute connected [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute eigrp process-id [ match { external | internal }] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute isis process-id [ level { 1 | 1-inter-area | 2 }] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute ospf process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute ospfv3 process-id [ match { external [ 1 | 2 ] | internal | nssa-external [ 1 | 2 ]}] [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute rip [ metric metric-value ] [ route-policy route-policy-name ]
                                                          • redistribute static [ metric metric-value ] [ route-policy route-policy-name ]


                                                          Example:
                                                          RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# redistribute eigrp 23 
                                                           

                                                          Configures redistribution of a protocol into the VRF address family context.

                                                          The redistribute command is used if BGP is not used between the PE-CE routers. If BGP is used between PE-CE routers, the IGP that is used has to be redistributed into BGP to establish VPN connectivity with other PE sites. Redistribution is also required for inter-table import and export.

                                                           
                                                          Step 6 Use the commit or end command.  

                                                          commit—Saves the configuration changes, and remains within the configuration session.

                                                          end—Prompts user to take one of these actions:
                                                          • Yes— Saves configuration changes and exits the configuration session.
                                                          • No—Exits the configuration session without committing the configuration changes.
                                                          • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                           

                                                          Configuring Keychains for BGP

                                                          Keychains provide secure authentication by supporting different MAC authentication algorithms and provide graceful key rollover. Perform this task to configure keychains for BGP. This task is optional.


                                                          Note


                                                          If a keychain is configured for a neighbor group or a session group, a neighbor using the group inherits the keychain. Values of commands configured specifically for a neighbor override inherited values.


                                                          SUMMARY STEPS

                                                            1.    configure

                                                            2.    router bgp as-number

                                                            3.    neighbor ip-address

                                                            4.    remote-as as-number

                                                            5.    keychain name

                                                            6.    Use the commit or end command.


                                                          DETAILED STEPS
                                                              Command or Action Purpose
                                                            Step 1 configure


                                                            Example:
                                                            RP/0/RSP0/CPU0:router# configure
                                                             

                                                            Enters global configuration mode.

                                                             
                                                            Step 2 router bgp as-number


                                                            Example:
                                                            RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                             

                                                            Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                             
                                                            Step 3 neighbor ip-address


                                                            Example:
                                                            RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                                             

                                                            Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                                             
                                                            Step 4 remote-as as-number


                                                            Example:
                                                            RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002
                                                             

                                                            Creates a neighbor and assigns a remote autonomous system number to it.

                                                             
                                                            Step 5 keychain name


                                                            Example:
                                                            RP/0/RSP0/CPU0:router(config-bgp-nbr)# keychain kych_a
                                                             

                                                            Configures keychain-based authentication.

                                                             
                                                            Step 6 Use the commit or end command.  

                                                            commit—Saves the configuration changes, and remains within the configuration session.

                                                            end—Prompts user to take one of these actions:
                                                            • Yes— Saves configuration changes and exits the configuration session.
                                                            • No—Exits the configuration session without committing the configuration changes.
                                                            • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                             

                                                            Disabling a BGP Neighbor

                                                            Perform this task to administratively shut down a neighbor session without removing the configuration.

                                                            SUMMARY STEPS

                                                              1.    configure

                                                              2.    router bgp as-number

                                                              3.    neighbor ip-address

                                                              4.    shutdown

                                                              5.    Use the commit or end command.


                                                            DETAILED STEPS
                                                                Command or Action Purpose
                                                              Step 1 configure


                                                              Example:
                                                              RP/0/RSP0/CPU0:router# configure
                                                               

                                                              Enters global configuration mode.

                                                               
                                                              Step 2 router bgp as-number


                                                              Example:
                                                              RP/0/RSP0/CPU0:router(config)# router bgp 127
                                                               

                                                              Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                               
                                                              Step 3 neighbor ip-address


                                                              Example:
                                                              RP/0/RSP0/CPU0:router(config-bgp)# neighbor 172.168.40.24
                                                               

                                                              Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                                               
                                                              Step 4 shutdown


                                                              Example:
                                                              RP/0/RSP0/CPU0:router(config-bgp-nbr)# shutdown
                                                               

                                                              Disables all active sessions for the specified neighbor.

                                                               
                                                              Step 5 Use the commit or end command.  

                                                              commit—Saves the configuration changes, and remains within the configuration session.

                                                              end—Prompts user to take one of these actions:
                                                              • Yes— Saves configuration changes and exits the configuration session.
                                                              • No—Exits the configuration session without committing the configuration changes.
                                                              • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                               

                                                              Resetting Neighbors Using BGP Inbound Soft Reset

                                                              Perform this task to trigger an inbound soft reset of the specified address families for the specified group or neighbors. The group is specified by the * , ip-address , as-number , or external keywords and arguments.

                                                              Resetting neighbors is useful if you change the inbound policy for the neighbors or any other configuration that affects the sending or receiving of routing updates. If an inbound soft reset is triggered, BGP sends a REFRESH request to the neighbor if the neighbor has advertised the ROUTE_REFRESH capability. To determine whether the neighbor has advertised the ROUTE_REFRESH capability, use the show bgp neighbors command.

                                                              SUMMARY STEPS

                                                                1.    show bgp neighbors

                                                                2.    clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } { * | ip-address | as as-number | external } soft  [ in [ prefix-filter ] | out ]


                                                              DETAILED STEPS
                                                                  Command or Action Purpose
                                                                Step 1 show bgp neighbors


                                                                Example:
                                                                RP/0/RSP0/CPU0:router# show bgp neighbors
                                                                 

                                                                Verifies that received route refresh capability from the neighbor is enabled.

                                                                 
                                                                Step 2 clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } { * | ip-address | as as-number | external } soft  [ in [ prefix-filter ] | out ]


                                                                Example:
                                                                RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast 10.0.0.1 soft in
                                                                 

                                                                Soft resets a BGP neighbor.

                                                                • The * keyword resets all BGP neighbors.
                                                                • The ip-address argument specifies the address of the neighbor to be reset.
                                                                • The as-number argument specifies that all neighbors that match the autonomous system number be reset.
                                                                • The external keyword specifies that all external neighbors are reset.
                                                                 

                                                                Resetting Neighbors Using BGP Outbound Soft Reset

                                                                Perform this task to trigger an outbound soft reset of the specified address families for the specified group or neighbors. The group is specified by the * , ip-address , as-number , or external keywords and arguments.

                                                                Resetting neighbors is useful if you change the outbound policy for the neighbors or any other configuration that affects the sending or receiving of routing updates.

                                                                If an outbound soft reset is triggered, BGP resends all routes for the address family to the given neighbors.

                                                                To determine whether the neighbor has advertised the ROUTE_REFRESH capability, use the show bgp neighbors command.

                                                                SUMMARY STEPS

                                                                  1.    show bgp neighbors

                                                                  2.    clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } { * | ip-address | as as-number | external } soft  [ in [ prefix-filter ] | ]


                                                                DETAILED STEPS
                                                                    Command or Action Purpose
                                                                  Step 1 show bgp neighbors


                                                                  Example:
                                                                  RP/0/RSP0/CPU0:router# show bgp neighbors
                                                                   

                                                                  Verifies that received route refresh capability from the neighbor is enabled.

                                                                   
                                                                  Step 2 clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } { * | ip-address | as as-number | external } soft  [ in [ prefix-filter ] | ]


                                                                  Example:
                                                                  RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast 10.0.0.2 soft out
                                                                   

                                                                  Soft resets a BGP neighbor.

                                                                  • The * keyword resets all BGP neighbors.
                                                                  • The ip-address argument specifies the address of the neighbor to be reset.
                                                                  • The as-number argument specifies that all neighbors that match the autonomous system number be reset.
                                                                  • The external keyword specifies that all external neighbors are reset.
                                                                   

                                                                  Resetting Neighbors Using BGP Hard Reset

                                                                  Perform this task to reset neighbors using a hard reset. A hard reset removes the TCP connection to the neighbor, removes all routes received from the neighbor from the BGP table, and then re-establishes the session with the neighbor. If the graceful keyword is specified, the routes from the neighbor are not removed from the BGP table immediately, but are marked as stale. After the session is re-established, any stale route that has not been received again from the neighbor is removed.

                                                                  SUMMARY STEPS

                                                                    1.    clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } | { * | ip-address | as as-number | external } [ graceful ] soft  [ in [ prefix-filter ] | out ]


                                                                  DETAILED STEPS
                                                                      Command or Action Purpose
                                                                    Step 1 clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } | { * | ip-address | as as-number | external } [ graceful ] soft  [ in [ prefix-filter ] | out ]


                                                                    Example:
                                                                    RP/0/RSP0/CPU0:router# clear bgp ipv4 unicast 10.0.0.3 graceful soft out
                                                                     

                                                                    Clears a BGP neighbor.

                                                                    • The * keyword resets all BGP neighbors.
                                                                    • The ip-address argument specifies the address of the neighbor to be reset.
                                                                    • The as-number argument specifies that all neighbors that match the autonomous system number be reset.
                                                                    • The external keyword specifies that all external neighbors are reset.

                                                                    The graceful keyword specifies a graceful restart.

                                                                     

                                                                    Clearing Caches, Tables, and Databases

                                                                    Perform this task to remove all contents of a particular cache, table, or database. The clear bgp command resets the sessions of the specified group of neighbors (hard reset); it removes the TCP connection to the neighbor, removes all routes received from the neighbor from the BGP table, and then re-establishes the session with the neighbor. Clearing a cache, table, or database can become necessary when the contents of the particular structure have become, or are suspected to be, invalid.

                                                                    SUMMARY STEPS

                                                                      1.    clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } ip-address

                                                                      2.    clear bgp external

                                                                      3.    clear bgp *


                                                                    DETAILED STEPS
                                                                        Command or Action Purpose
                                                                      Step 1 clear bgp { ipv4 { unicast | multicast | all | tunnel } | ipv6 unicast | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } { ipv4 unicast | ipv6 unicast } ip-address


                                                                      Example:
                                                                      RP/0/RSP0/CPU0:router# clear bgp ipv4 172.20.1.1
                                                                       

                                                                      Clears a specified neighbor.

                                                                       
                                                                      Step 2 clear bgp external


                                                                      Example:
                                                                      RP/0/RSP0/CPU0:router# clear bgp external
                                                                       

                                                                      Clears all external peers.

                                                                       
                                                                      Step 3 clear bgp *


                                                                      Example:
                                                                      RP/0/RSP0/CPU0:router# clear bgp *
                                                                       

                                                                      Clears all BGP neighbors.

                                                                       

                                                                      Displaying System and Network Statistics

                                                                      Perform this task to display specific statistics, such as the contents of BGP routing tables, caches, and databases. Information provided can be used to determine resource usage and solve network problems. You can also display information about node reachability and discover the routing path that the packets of your device are taking through the network.

                                                                      SUMMARY STEPS

                                                                        1.    show bgp cidr-only

                                                                        2.    show bgp community community-list [ exact-match ]

                                                                        3.    show bgp regexp regular-expression

                                                                        4.    show bgp

                                                                        5.    show bgp neighbors ip-address [ advertised-routes | dampened-routes | flap-statistics | performance-statistics | received prefix-filter | routes ]

                                                                        6.    show bgp paths

                                                                        7.    show bgp neighbor-group group-name configuration

                                                                        8.    show bgp summary


                                                                      DETAILED STEPS
                                                                          Command or Action Purpose
                                                                        Step 1 show bgp cidr-only


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp cidr-only
                                                                         

                                                                        Displays routes with nonnatural network masks (classless interdomain routing [CIDR]) routes.

                                                                         
                                                                        Step 2 show bgp community community-list [ exact-match ]


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp community 1081:5 exact-match
                                                                         

                                                                        Displays routes that match the specified BGP community.

                                                                         
                                                                        Step 3 show bgp regexp regular-expression


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp regexp "^3 "
                                                                         

                                                                        Displays routes that match the specified autonomous system path regular expression.

                                                                         
                                                                        Step 4 show bgp


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp
                                                                         

                                                                        Displays entries in the BGP routing table.

                                                                         
                                                                        Step 5 show bgp neighbors ip-address [ advertised-routes | dampened-routes | flap-statistics | performance-statistics | received prefix-filter | routes ]


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp neighbors 10.0.101.1
                                                                         

                                                                        Displays information about the BGP connection to the specified neighbor.

                                                                        • The advertised-routes keyword displays all routes the router advertised to the neighbor.
                                                                        • The dampened-routes keyword displays the dampened routes that are learned from the neighbor.
                                                                        • The flap-statistics keyword displays flap statistics of the routes learned from the neighbor.
                                                                        • The performance-statistics keyword displays performance statistics relating to work done by the BGP process for this neighbor.
                                                                        • The received prefix-filter keyword and argument display the received prefix list filter.
                                                                        • The routes keyword displays routes learned from the neighbor.
                                                                         
                                                                        Step 6 show bgp paths


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp paths
                                                                         

                                                                        Displays all BGP paths in the database.

                                                                         
                                                                        Step 7 show bgp neighbor-group group-name configuration


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp neighbor-group group_1 configuration
                                                                         

                                                                        Displays the effective configuration for a specified neighbor group, including any configuration inherited by this neighbor group.

                                                                         
                                                                        Step 8 show bgp summary


                                                                        Example:
                                                                        RP/0/RSP0/CPU0:router# show bgp summary
                                                                         

                                                                        Displays the status of all BGP connections.

                                                                         

                                                                        Displaying BGP Process Information

                                                                        Perform this task to display specific BGP process information.

                                                                        SUMMARY STEPS

                                                                          1.    show bgp process

                                                                          2.    show bgp ipv4 unicast summary

                                                                          3.    show bgp vpnv4 unicast summary

                                                                          4.    show bgp vrf ( vrf-name | all }

                                                                          5.    show bgp process detail

                                                                          6.    show bgp summary

                                                                          7.    show placement program bgp

                                                                          8.    show placement program brib


                                                                        DETAILED STEPS
                                                                            Command or Action Purpose
                                                                          Step 1 show bgp process


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show bgp process
                                                                           

                                                                          Displays status and summary information for the BGP process. The output shows various global and address family-specific BGP configurations. A summary of the number of neighbors, update messages, and notification messages sent and received by the process is also displayed.

                                                                           
                                                                          Step 2 show bgp ipv4 unicast summary


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show bgp ipv4 unicast summary
                                                                           

                                                                          Displays a summary of the neighbors for the IPv4 unicast address family.

                                                                           
                                                                          Step 3 show bgp vpnv4 unicast summary


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show bgp vpnv4 unicast summary
                                                                           

                                                                          Displays a summary of the neighbors for the VPNv4 unicast address family.

                                                                           
                                                                          Step 4 show bgp vrf ( vrf-name | all }


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show bgp vrf vrf_A
                                                                           

                                                                          Displays BGP VPN virtual routing and forwarding (VRF) information.

                                                                           
                                                                          Step 5 show bgp process detail


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show bgp processes detail
                                                                           

                                                                          Displays detailed process information including the memory used by each of various internal structure types.

                                                                           
                                                                          Step 6 show bgp summary


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show bgp summary
                                                                           

                                                                          Displays the status of all BGP connections.

                                                                           
                                                                          Step 7 show placement program bgp


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show placement program bgp
                                                                           

                                                                          Displays BGP program information.

                                                                          • If a program is shown as having ‘rejected locations’ (for example, locations where program cannot be placed), the locations in question can be viewed using the show placement program bgp command.
                                                                          • If a program has been placed but not started, the amount of elapsed time since the program was placed is displayed in the Waiting to start column.
                                                                           
                                                                          Step 8 show placement program brib


                                                                          Example:
                                                                          RP/0/RSP0/CPU0:router# show placement program brib
                                                                           

                                                                          Displays bRIB program information.

                                                                          • If a program is shown as having ‘rejected locations’ (for example, locations where program cannot be placed), the locations in question can be viewed using the show placement program bgp command.
                                                                          • If a program has been placed but not started, the amount of elapsed time since the program was placed is displayed in the Waiting to start column.
                                                                           

                                                                          Monitoring BGP Update Groups

                                                                          This task displays information related to the processing of BGP update groups.

                                                                          SUMMARY STEPS

                                                                            1.    show bgp [ ipv4 { unicast | multicast | all | tunnel } | ipv6 { unicast | all } | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } [ ipv4 unicast ] update-group [ neighbor ip-address | process-id.index [ summary | performance-statistics ]]


                                                                          DETAILED STEPS
                                                                              Command or Action Purpose
                                                                            Step 1 show bgp [ ipv4 { unicast | multicast | all | tunnel } | ipv6 { unicast | all } | all { unicast | multicast | all | tunnel } | vpnv4 unicast | vrf { vrf-name | all } [ ipv4 unicast ] update-group [ neighbor ip-address | process-id.index [ summary | performance-statistics ]]


                                                                            Example:
                                                                            RP/0/RSP0/CPU0:router# show bgp update-group 0.0
                                                                             

                                                                            Displays information about BGP update groups.

                                                                            • The ip-address argument displays the update groups to which that neighbor belongs.
                                                                            • The process-id.index argument selects a particular update group to display and is specified as follows: process ID (dot) index. Process ID range is from 0 to 254. Index range is from 0 to 4294967295.
                                                                            • The summary keyword displays summary information for neighbors in a particular update group.
                                                                            • If no argument is specified, this command displays information for all update groups (for the specified address family).
                                                                            • The performance-statistics keyword displays performance statistics for an update group.
                                                                             

                                                                            Configuring BGP Nonstop Routing

                                                                            Perform this task to configure BGP Nonstop Routing (NSR).

                                                                            SUMMARY STEPS

                                                                              1.    configure

                                                                              2.    router bgp as-number

                                                                              3.    nsr

                                                                              4.    Use the commit or end command.


                                                                            DETAILED STEPS
                                                                                Command or Action Purpose
                                                                              Step 1 configure


                                                                              Example:
                                                                              RP/0/RSP0/CPU0:router# configure
                                                                               

                                                                              Enters global configuration mode.

                                                                               
                                                                              Step 2 router bgp as-number


                                                                              Example:
                                                                              RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                                               

                                                                              Specifies the BGP AS number, and enters the BGP configuration mode, for configuring BGP routing processes.

                                                                               
                                                                              Step 3 nsr


                                                                              Example:
                                                                              RP/0/RSP0/CPU0:router(config-bgp)# nsr 
                                                                               

                                                                              Activates BGP Nonstop routing.

                                                                              Note   

                                                                              BGP supports 5000 NSR sessions.

                                                                               
                                                                              Step 4 Use the commit or end command.  

                                                                              commit—Saves the configuration changes, and remains within the configuration session.

                                                                              end—Prompts user to take one of these actions:
                                                                              • Yes— Saves configuration changes and exits the configuration session.
                                                                              • No—Exits the configuration session without committing the configuration changes.
                                                                              • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                               

                                                                              Installing Primary Backup Path for Prefix Independent Convergence (PIC)

                                                                              Perform the following tasks to install a backup path into the forwarding table and provide prefix independent convergence (PIC) in case of a PE-CE link failure:

                                                                              SUMMARY STEPS

                                                                                1.    configure

                                                                                2.    router bgp as-number

                                                                                3.    Do one of the following

                                                                                • address-family {vpnv4 unicast | vpnv6 unicast}
                                                                                • vrf vrf-name {ipv4 unicast | ipv6 unicast}

                                                                                4.    additional-paths selection route-policy route-policy-name

                                                                                5.    Use the commit or end command.


                                                                              DETAILED STEPS
                                                                                  Command or Action Purpose
                                                                                Step 1 configure


                                                                                Example:
                                                                                RP/0/RSP0/CPU0:router# configure
                                                                                 

                                                                                Enters global configuration mode.

                                                                                 
                                                                                Step 2 router bgp as-number


                                                                                Example:
                                                                                RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                 

                                                                                Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                 
                                                                                Step 3 Do one of the following
                                                                                • address-family {vpnv4 unicast | vpnv6 unicast}
                                                                                • vrf vrf-name {ipv4 unicast | ipv6 unicast}


                                                                                Example:
                                                                                RP/0/RSP0/CPU0:router(config-bgp)# address-family vpnv4 unicast
                                                                                 

                                                                                Specifies the address family or VRF address family and enters the address family or VRF address family configuration submode.

                                                                                 
                                                                                Step 4 additional-paths selection route-policy route-policy-name


                                                                                Example:
                                                                                RP/0/RSP0/CPU0:router(config-bgp-af)# additional-paths selection route-policy ap1
                                                                                 
                                                                                Configures additional paths selection mode for a prefix.
                                                                                Note   

                                                                                Use the additional-paths selection command with an appropriate route-policy to calculate backup paths and to enable Prefix Independent Convergence (PIC) functionality.

                                                                                The route-policy configuration is a pre-requisite for configuring the additional-paths selection mode for a prefix . This is an example route-policy configuration to use with additional-selection command:
                                                                                route-policy ap1
                                                                                    set path-selection backup 1 install
                                                                                  end-policy
                                                                                
                                                                                 
                                                                                Step 5 Use the commit or end command.  

                                                                                commit—Saves the configuration changes, and remains within the configuration session.

                                                                                end—Prompts user to take one of these actions:
                                                                                • Yes— Saves configuration changes and exits the configuration session.
                                                                                • No—Exits the configuration session without committing the configuration changes.
                                                                                • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                 

                                                                                Retaining Allocated Local Label for Primary Path

                                                                                Perform the following tasks to retain the previously allocated local label for the primary path on the primary PE for some configurable time after reconvergence:

                                                                                SUMMARY STEPS

                                                                                  1.    configure

                                                                                  2.    router bgp as-number

                                                                                  3.    address-family { vpnv4 unicast | vpnv6 unicast }

                                                                                  4.    retain local-label minutes

                                                                                  5.    Use the commit or end command.


                                                                                DETAILED STEPS
                                                                                    Command or Action Purpose
                                                                                  Step 1 configure


                                                                                  Example:
                                                                                  RP/0/RSP0/CPU0:router# configure
                                                                                   

                                                                                  Enters global configuration mode.

                                                                                   
                                                                                  Step 2 router bgp as-number


                                                                                  Example:
                                                                                  RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                   

                                                                                  Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                   
                                                                                  Step 3 address-family { vpnv4 unicast | vpnv6 unicast }


                                                                                  Example:
                                                                                  RP/0/RSP0/CPU0:router(config-bgp)# address-family vpnv4 unicast
                                                                                   

                                                                                  Specifies the address family and enters the address family configuration submode.

                                                                                   
                                                                                  Step 4 retain local-label minutes


                                                                                  Example:
                                                                                  RP/0/RSP0/CPU0:router(config-bgp-af)# retain local-label 10
                                                                                   

                                                                                  Retains the previously allocated local label for the primary path on the primary PE for 10 minutes after reconvergence.

                                                                                   
                                                                                  Step 5 Use the commit or end command.  

                                                                                  commit—Saves the configuration changes, and remains within the configuration session.

                                                                                  end—Prompts user to take one of these actions:
                                                                                  • Yes— Saves configuration changes and exits the configuration session.
                                                                                  • No—Exits the configuration session without committing the configuration changes.
                                                                                  • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                   

                                                                                  Configuring BGP Additional Paths

                                                                                  Perform these tasks to configure BGP Additional Paths capability:

                                                                                  SUMMARY STEPS

                                                                                    1.    configure

                                                                                    2.    route-policy route-policy-name

                                                                                    3.    if conditional-expression then action-statement else

                                                                                    4.    pass endif

                                                                                    5.    end-policy

                                                                                    6.    router bgp as-number

                                                                                    7.    address-family {ipv4 {unicast | multicast} | ipv6 {unicast | multicast | l2vpn vpls-vpws | vpnv4 unicast | vpnv6 unicast }

                                                                                    8.    additional-paths receive

                                                                                    9.    additional-paths send

                                                                                    10.    additional-paths selection route-policy route-policy-name

                                                                                    11.    Use the commit or end command.


                                                                                  DETAILED STEPS
                                                                                      Command or Action Purpose
                                                                                    Step 1 configure


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router# configure
                                                                                     

                                                                                    Enters global configuration mode.

                                                                                     
                                                                                    Step 2 route-policy route-policy-name


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router (config)#route-policy add_path_policy
                                                                                     

                                                                                    Defines the route policy and enters route-policy configuration mode.

                                                                                     
                                                                                    Step 3 if conditional-expression then action-statement else


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router (config-rpl)#if community matches-any (*) then
                                                                                        set path-selection all advertise
                                                                                      else
                                                                                     

                                                                                    Decides the actions and dispositions for the given route.

                                                                                     
                                                                                    Step 4 pass endif


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config-rpl-else)#pass
                                                                                    RP/0/RSP0/CPU0:router(config-rpl-else)#endif
                                                                                    
                                                                                     

                                                                                    Passes the route for processing and ends the if statement.

                                                                                     
                                                                                    Step 5 end-policy


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config-rpl)#end-policy
                                                                                     

                                                                                    Ends the route policy definition of the route policy and exits route-policy configuration mode.

                                                                                     
                                                                                    Step 6 router bgp as-number


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config)#router bgp 100
                                                                                     

                                                                                    Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                     
                                                                                    Step 7 address-family {ipv4 {unicast | multicast} | ipv6 {unicast | multicast | l2vpn vpls-vpws | vpnv4 unicast | vpnv6 unicast }

                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config-bgp)#address-family ipv4 unicast
                                                                                     

                                                                                    Specifies the address family and enters address family configuration submode.

                                                                                     
                                                                                    Step 8 additional-paths receive


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config-bgp-af)#additional-paths receive
                                                                                     

                                                                                    Configures receive capability of multiple paths for a prefix to the capable peers.

                                                                                     
                                                                                    Step 9 additional-paths send


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config-bgp-af)#additional-paths send
                                                                                     

                                                                                    Configures send capability of multiple paths for a prefix to the capable peers .

                                                                                     
                                                                                    Step 10 additional-paths selection route-policy route-policy-name


                                                                                    Example:
                                                                                    RP/0/RSP0/CPU0:router(config-bgp-af)#additional-paths selection route-policy add_path_policy
                                                                                     

                                                                                    Configures additional paths selection capability for a prefix.

                                                                                     
                                                                                    Step 11 Use the commit or end command.  

                                                                                    commit—Saves the configuration changes, and remains within the configuration session.

                                                                                    end—Prompts user to take one of these actions:
                                                                                    • Yes— Saves configuration changes and exits the configuration session.
                                                                                    • No—Exits the configuration session without committing the configuration changes.
                                                                                    • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                     

                                                                                    Configuring iBGP Multipath Load Sharing

                                                                                    Perform this task to configure the iBGP Multipath Load Sharing:

                                                                                    SUMMARY STEPS

                                                                                      1.    configure

                                                                                      2.    router bgp as-number

                                                                                      3.    address-family {ipv4|ipv6} {unicast|multicast}

                                                                                      4.    maximum-paths ibgp number

                                                                                      5.    Use the commit or end command.


                                                                                    DETAILED STEPS
                                                                                        Command or Action Purpose
                                                                                      Step 1 configure


                                                                                      Example:
                                                                                      RP/0/RSP0/CPU0:router# configure
                                                                                       

                                                                                      Enters global configuration mode.

                                                                                       
                                                                                      Step 2 router bgp as-number


                                                                                      Example:
                                                                                      RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                       

                                                                                      Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                       
                                                                                      Step 3 address-family {ipv4|ipv6} {unicast|multicast}

                                                                                      Example:
                                                                                      RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 multicast
                                                                                       

                                                                                      Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                                                                                       
                                                                                      Step 4 maximum-paths ibgp number


                                                                                      Example:
                                                                                      RP/0/RSP0/CPU0:router(config-bgp-af)# maximum-paths ibgp 30
                                                                                       

                                                                                      Configures the maximum number of iBGP paths for load sharing.

                                                                                       
                                                                                      Step 5 Use the commit or end command.  

                                                                                      commit—Saves the configuration changes, and remains within the configuration session.

                                                                                      end—Prompts user to take one of these actions:
                                                                                      • Yes— Saves configuration changes and exits the configuration session.
                                                                                      • No—Exits the configuration session without committing the configuration changes.
                                                                                      • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                       

                                                                                      Originating Prefixes with AiGP

                                                                                      Perform this task to configure origination of routes with the AiGP metric:

                                                                                      Before You Begin

                                                                                      Origination of routes with the accumulated interior gateway protocol (AiGP) metric is controlled by configuration. AiGP attributes are attached to redistributed routes that satisfy following conditions:

                                                                                      • The protocol redistributing the route is enabled for AiGP.
                                                                                      • The route is an interior gateway protocol (iGP) route redistributed into border gateway protocol (BGP). The value assigned to the AiGP attribute is the value of iGP next hop to the route or as set by a route-policy.
                                                                                      • The route is a static route redistributed into BGP. The value assigned is the value of next hop to the route or as set by a route-policy.
                                                                                      • The route is imported into BGP through network statement. The value assigned is the value of next hop to the route or as set by a route-policy.
                                                                                      SUMMARY STEPS

                                                                                        1.    configure

                                                                                        2.    route-policy aigp_policy

                                                                                        3.    set aigp-metricigp-cost

                                                                                        4.    exit

                                                                                        5.    router bgp as-number

                                                                                        6.    address-family {ipv4 | ipv6} unicast

                                                                                        7.    redistribute ospf osp route-policy plcy_namemetric value

                                                                                        8.    Use the commit or end command.


                                                                                      DETAILED STEPS
                                                                                          Command or Action Purpose
                                                                                        Step 1 configure


                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router# configure
                                                                                         

                                                                                        Enters global configuration mode.

                                                                                         
                                                                                        Step 2 route-policy aigp_policy


                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router(config)# route-policy aip_policy
                                                                                         

                                                                                        Enters route-policy configuration mode and sets the route-policy

                                                                                         
                                                                                        Step 3 set aigp-metricigp-cost


                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router(config-rpl)# set aigp-metric igp-cost
                                                                                         

                                                                                        Sets the internal routing protocol cost as the aigp metric.

                                                                                         
                                                                                        Step 4 exit


                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router(config-rpl)# exit
                                                                                         

                                                                                        Exits route-policy configuration mode.

                                                                                         
                                                                                        Step 5 router bgp as-number


                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                         

                                                                                        Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                         
                                                                                        Step 6 address-family {ipv4 | ipv6} unicast

                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
                                                                                         

                                                                                        Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

                                                                                         
                                                                                        Step 7 redistribute ospf osp route-policy plcy_namemetric value


                                                                                        Example:
                                                                                        RP/0/RSP0/CPU0:router(config-bgp-af)#redistribute ospf osp route-policy aigp_policy metric 1
                                                                                         

                                                                                        Allows the redistribution of AiBGP metric into OSPF.

                                                                                         
                                                                                        Step 8 Use the commit or end command.  

                                                                                        commit—Saves the configuration changes, and remains within the configuration session.

                                                                                        end—Prompts user to take one of these actions:
                                                                                        • Yes— Saves configuration changes and exits the configuration session.
                                                                                        • No—Exits the configuration session without committing the configuration changes.
                                                                                        • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                         

                                                                                        Configuring BGP Accept Own

                                                                                        Perform this task to configure BGP Accept Own:

                                                                                        SUMMARY STEPS

                                                                                          1.    configure

                                                                                          2.    router bgp as-number

                                                                                          3.    neighbor ip-address

                                                                                          4.    remote-as as-number

                                                                                          5.    update-source type interface-path-id

                                                                                          6.    address-family {vpnv4 unicast | vpnv6 unicast}

                                                                                          7.    accept-own [inheritance-disable]


                                                                                        DETAILED STEPS
                                                                                            Command or Action Purpose
                                                                                          Step 1 configure


                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router# configure
                                                                                           

                                                                                          Enters global configuration mode.

                                                                                           
                                                                                          Step 2 router bgp as-number


                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router(config)#router bgp 100
                                                                                           

                                                                                          Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                           
                                                                                          Step 3 neighbor ip-address


                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router(config-bgp)#neighbor 10.1.2.3
                                                                                           

                                                                                          Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                                                                           
                                                                                          Step 4 remote-as as-number


                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router(config-bgp-nbr)#remote-as 100
                                                                                           

                                                                                          Assigns a remote autonomous system number to the neighbor.

                                                                                           
                                                                                          Step 5 update-source type interface-path-id


                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router(config-bgp-nbr)#update-source Loopback0
                                                                                           

                                                                                          Allows sessions to use the primary IP address from a specific interface as the local address when forming a session with a neighbor.

                                                                                           
                                                                                          Step 6 address-family {vpnv4 unicast | vpnv6 unicast}

                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router(config-bgp-nbr)#address-family vpnv6 unicast
                                                                                           

                                                                                          Specifies the address family as VPNv4 or VPNv6 and enters neighbor address family configuration mode.

                                                                                           
                                                                                          Step 7 accept-own [inheritance-disable]

                                                                                          Example:
                                                                                          RP/0/RSP0/CPU0:router(config-bgp-nbr-af)#accept-own
                                                                                           

                                                                                          Enables handling of self-originated VPN routes containing Accept_Own community.

                                                                                          Use the inheritance-disable keyword to disable the "accept own" configuration and to prevent inheritance of "acceptown" from a parent configuration.

                                                                                           

                                                                                          Configuring BGP Link-State

                                                                                          Configuring BGP Link-state

                                                                                          To exchange BGP link-state (LS) information with a BGP neighbor, perform these steps:

                                                                                          SUMMARY STEPS

                                                                                            1.    configure

                                                                                            2.    router bgp as-number

                                                                                            3.    neighbor ip-address

                                                                                            4.    remote-as as-number

                                                                                            5.    address-family link-state link-state

                                                                                            6.    Use the commit or end command.


                                                                                          DETAILED STEPS
                                                                                              Command or Action Purpose
                                                                                            Step 1 configure


                                                                                            Example:
                                                                                            RP/0/RSP0/CPU0:router# configure
                                                                                             

                                                                                            Enters global configuration mode.

                                                                                             
                                                                                            Step 2 router bgp as-number


                                                                                            Example:
                                                                                            RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                            
                                                                                            
                                                                                             

                                                                                            Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                             
                                                                                            Step 3 neighbor ip-address


                                                                                            Example:
                                                                                            RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.0.2
                                                                                            
                                                                                            
                                                                                             

                                                                                            Configures a CE neighbor. The ip-address argument must be a private address.

                                                                                             
                                                                                            Step 4 remote-as as-number


                                                                                            Example:
                                                                                            RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
                                                                                            
                                                                                            
                                                                                             

                                                                                            Configures the remote AS for the CE neighbor.

                                                                                             
                                                                                            Step 5 address-family link-state link-state


                                                                                            Example:
                                                                                            RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family link-state link-state
                                                                                            
                                                                                            
                                                                                             

                                                                                            Distributes BGP link-state information to the specified neighbor.

                                                                                             
                                                                                            Step 6 Use the commit or end command.  

                                                                                            commit—Saves the configuration changes, and remains within the configuration session.

                                                                                            end—Prompts user to take one of these actions:
                                                                                            • Yes— Saves configuration changes and exits the configuration session.
                                                                                            • No—Exits the configuration session without committing the configuration changes.
                                                                                            • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                             

                                                                                            Configuring Domain Distinguisher

                                                                                            To configure unique identifier four-octet ASN, perform these steps:

                                                                                            SUMMARY STEPS

                                                                                              1.    configure

                                                                                              2.    router bgp as-number

                                                                                              3.    address-family link-state link-state

                                                                                              4.    domain-distinguisher unique-id

                                                                                              5.    Use the commit or end command.


                                                                                            DETAILED STEPS
                                                                                                Command or Action Purpose
                                                                                              Step 1 configure


                                                                                              Example:
                                                                                              RP/0/RSP0/CPU0:router# configure
                                                                                               

                                                                                              Enters global configuration mode.

                                                                                               
                                                                                              Step 2 router bgp as-number


                                                                                              Example:
                                                                                              RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                              
                                                                                              
                                                                                               

                                                                                              Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                               
                                                                                              Step 3 address-family link-state link-state


                                                                                              Example:
                                                                                              RP/0/RSP0/CPU0:router(config-bgp)# address-family link-state link-state
                                                                                              
                                                                                              
                                                                                               

                                                                                              Enters address-family link-state configuration mode.

                                                                                               
                                                                                              Step 4 domain-distinguisher unique-id


                                                                                              Example:
                                                                                              RP/0/RSP0/CPU0:router(config-bgp-af)# domain-distinguisher 1234
                                                                                              
                                                                                              
                                                                                               

                                                                                              Configures unique identifier four-octet ASN. Range is from 1 to 4294967295.

                                                                                               
                                                                                              Step 5 Use the commit or end command.  

                                                                                              commit—Saves the configuration changes, and remains within the configuration session.

                                                                                              end—Prompts user to take one of these actions:
                                                                                              • Yes— Saves configuration changes and exits the configuration session.
                                                                                              • No—Exits the configuration session without committing the configuration changes.
                                                                                              • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                               

                                                                                              Configuring BGP Permanent Network

                                                                                              Configuring BGP Permanent Network

                                                                                              Perform this task to configure BGP permanent network. You must configure at least one route-policy to identify the set of prefixes (networks) for which the permanent network (path) is to be configured.

                                                                                              SUMMARY STEPS

                                                                                                1.    configure

                                                                                                2.    prefix-set prefix-set-name

                                                                                                3.    exit

                                                                                                4.    route-policy route-policy-name

                                                                                                5.    end-policy

                                                                                                6.    router bgp as-number

                                                                                                7.    address-family { ipv4 | ipv6 } unicast

                                                                                                8.    permanent-network route-policy route-policy-name

                                                                                                9.    Use the commit or end command.

                                                                                                10.    show bgp {ipv4 | ipv6} unicast prefix-set


                                                                                              DETAILED STEPS
                                                                                                  Command or Action Purpose
                                                                                                Step 1 configure


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router# configure
                                                                                                 

                                                                                                Enters global configuration mode.

                                                                                                 
                                                                                                Step 2 prefix-set prefix-set-name


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config)# prefix-set PERMANENT-NETWORK-IPv4
                                                                                                RP/0/RSP0/CPU0:router(config-pfx)# 1.1.1.1/32,
                                                                                                RP/0/RSP0/CPU0:router(config-pfx)# 2.2.2.2/32,
                                                                                                RP/0/RSP0/CPU0:router(config-pfx)# 3.3.3.3/32
                                                                                                RP/0/RSP0/CPU0:router(config-pfx)# end-set
                                                                                                
                                                                                                
                                                                                                 

                                                                                                Enters prefix set configuration mode and defines a prefix set for contiguous and non-contiguous set of bits.

                                                                                                 
                                                                                                Step 3 exit


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config-pfx)# exit
                                                                                                
                                                                                                
                                                                                                 

                                                                                                Exits prefix set configuration mode and enters global configuration mode.

                                                                                                 
                                                                                                Step 4 route-policy route-policy-name


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config)# route-policy POLICY-PERMANENT-NETWORK-IPv4
                                                                                                RP/0/RSP0/CPU0:router(config-rpl)# if destination in PERMANENT-NETWORK-IPv4 then
                                                                                                RP/0/RSP0/CPU0:router(config-rpl)# pass
                                                                                                RP/0/RSP0/CPU0:router(config-rpl)# endif
                                                                                                 
                                                                                                
                                                                                                 

                                                                                                Creates a route policy and enters route policy configuration mode, where you can define the route policy.

                                                                                                 
                                                                                                Step 5 end-policy


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config-rpl)# end-policy
                                                                                                
                                                                                                
                                                                                                 

                                                                                                Ends the definition of a route policy and exits route policy configuration mode.

                                                                                                 
                                                                                                Step 6 router bgp as-number


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                                
                                                                                                
                                                                                                 

                                                                                                Specifies the autonomous system number and enters the BGP configuration mode.

                                                                                                 
                                                                                                Step 7 address-family { ipv4 | ipv6 } unicast


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
                                                                                                
                                                                                                
                                                                                                 

                                                                                                Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                                                                                 
                                                                                                Step 8 permanent-network route-policy route-policy-name


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:router(config-bgp-af)# permanent-network route-policy POLICY-PERMANENT-NETWORK-IPv4
                                                                                                
                                                                                                
                                                                                                 

                                                                                                Configures the permanent network (path) for the set of prefixes as defined in the route-policy.

                                                                                                 
                                                                                                Step 9 Use the commit or end command.  

                                                                                                commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                end—Prompts user to take one of these actions:
                                                                                                • Yes— Saves configuration changes and exits the configuration session.
                                                                                                • No—Exits the configuration session without committing the configuration changes.
                                                                                                • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                 
                                                                                                Step 10 show bgp {ipv4 | ipv6} unicast prefix-set


                                                                                                Example:
                                                                                                RP/0/RSP0/CPU0:routershow bgp ipv4 unicast 
                                                                                                
                                                                                                
                                                                                                 

                                                                                                (Optional) Displays whether the prefix-set is a permanent network in BGP.

                                                                                                 

                                                                                                How to Advertise Permanent Network

                                                                                                Perform this task to identify the peers to whom the permanent paths must be advertised.

                                                                                                SUMMARY STEPS

                                                                                                  1.    configure

                                                                                                  2.    router bgp as-number

                                                                                                  3.    neighbor ip-address

                                                                                                  4.    remote-as as-number

                                                                                                  5.    address-family { ipv4 | ipv6 } unicast

                                                                                                  6.    advertise permanent-network

                                                                                                  7.    Use the commit or end command.

                                                                                                  8.    show bgp {ipv4 | ipv6} unicast neighbor ip-address


                                                                                                DETAILED STEPS
                                                                                                    Command or Action Purpose
                                                                                                  Step 1 configure


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:router# configure
                                                                                                   

                                                                                                  Enters global configuration mode.

                                                                                                   
                                                                                                  Step 2 router bgp as-number


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:router(config)# router bgp 100
                                                                                                  
                                                                                                  
                                                                                                   

                                                                                                  Specifies the autonomous system number and enters the BGP configuration mode.

                                                                                                   
                                                                                                  Step 3 neighbor ip-address


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.255.255.254
                                                                                                  
                                                                                                  
                                                                                                   

                                                                                                  Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

                                                                                                   
                                                                                                  Step 4 remote-as as-number


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 4713
                                                                                                  
                                                                                                  
                                                                                                   

                                                                                                  Assigns the neighbor a remote autonomous system number.

                                                                                                   
                                                                                                  Step 5 address-family { ipv4 | ipv6 } unicast


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
                                                                                                  
                                                                                                  
                                                                                                   

                                                                                                  Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                                                                                   
                                                                                                  Step 6 advertise permanent-network


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# advertise permanent-network
                                                                                                  
                                                                                                  
                                                                                                   

                                                                                                  Specifies the peers to whom the permanent network (path) is advertised.

                                                                                                   
                                                                                                  Step 7 Use the commit or end command.  

                                                                                                  commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                  end—Prompts user to take one of these actions:
                                                                                                  • Yes— Saves configuration changes and exits the configuration session.
                                                                                                  • No—Exits the configuration session without committing the configuration changes.
                                                                                                  • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                   
                                                                                                  Step 8 show bgp {ipv4 | ipv6} unicast neighbor ip-address


                                                                                                  Example:
                                                                                                  RP/0/RSP0/CPU0:routershow bgp ipv4 unicast neighbor 10.255.255.254
                                                                                                  
                                                                                                  
                                                                                                   

                                                                                                  (Optional) Displays whether the neighbor is capable of receiving BGP permanent networks.

                                                                                                   

                                                                                                  Enabling BGP Unequal Cost Recursive Load Balancing

                                                                                                  Perform this task to enable unequal cost recursive load balancing for external BGP (eBGP), interior BGP (iBGP), and eiBGP and to enable BGP to carry link bandwidth attribute of the demilitarized zone (DMZ) link.

                                                                                                  When the PE router includes the link bandwidth extended community in its updates to the remote PE through the Multiprotocol Interior BGP (MP-iBGP) session (either IPv4 or VPNv4), the remote PE automatically does load balancing if the maximum-paths command is enabled.

                                                                                                  Unequal cost recursive load balancing happens across maximum eight paths only.


                                                                                                  Note


                                                                                                  Enabling BGP unequal cost recursive load balancing feature is not supported on CPP based cards.


                                                                                                  SUMMARY STEPS

                                                                                                    1.    configure

                                                                                                    2.    router bgp as-number

                                                                                                    3.    address-family { ipv4 | ipv6 } unicast

                                                                                                    4.    maximum-paths { ebgp | ibgp | eibgp } maximum [ unequal-cost ]

                                                                                                    5.    exit

                                                                                                    6.    neighbor ip-address

                                                                                                    7.    dmz-link-bandwidth

                                                                                                    8.    Use the commit or end command.


                                                                                                  DETAILED STEPS
                                                                                                      Command or Action Purpose
                                                                                                    Step 1 configure


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router# configure
                                                                                                     

                                                                                                    Enters global configuration mode.

                                                                                                     
                                                                                                    Step 2 router bgp as-number


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router(config)# router bgp 120
                                                                                                     

                                                                                                    Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                                     
                                                                                                    Step 3 address-family { ipv4 | ipv6 } unicast


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router(config-vrf)# address-family ipv4 unicast
                                                                                                     

                                                                                                    Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

                                                                                                    To see a list of all the possible keywords and arguments for this command, use the CLI help (?).

                                                                                                     
                                                                                                    Step 4 maximum-paths { ebgp | ibgp | eibgp } maximum [ unequal-cost ]


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# maximum-paths ebgp 3
                                                                                                     

                                                                                                    Configures the maximum number of parallel routes that BGP installs in the routing table.

                                                                                                    Note   

                                                                                                    Valid values for maximum-paths are eight, inclusive.

                                                                                                    • ebgp maximum : Consider only eBGP paths for multipath.
                                                                                                    • ibgp maximum [ unequal-cost ]: Consider load balancing between iBGP learned paths.
                                                                                                    • eibgp maximum : Consider both eBGP and iBGP learned paths for load balancing. eiBGP load balancing always does unequal-cost load balancing.

                                                                                                    When eiBGP is applied, eBGP or iBGP load balancing cannot be configured; however, eBGP and iBGP load balancing can coexist.

                                                                                                     
                                                                                                    Step 5 exit


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# exit
                                                                                                     

                                                                                                    Exits the current configuration mode.

                                                                                                     
                                                                                                    Step 6 neighbor ip-address


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 10.0.0.0
                                                                                                     

                                                                                                    Configures a CE neighbor. The ip-address argument must be a private address.

                                                                                                     
                                                                                                    Step 7 dmz-link-bandwidth


                                                                                                    Example:
                                                                                                    RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# dmz-link-bandwidth
                                                                                                     

                                                                                                    Originates a demilitarized-zone (DMZ) link-bandwidth extended community for the link to an eBGP/iBGP neighbor.

                                                                                                     
                                                                                                    Step 8 Use the commit or end command.  

                                                                                                    commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                    end—Prompts user to take one of these actions:
                                                                                                    • Yes— Saves configuration changes and exits the configuration session.
                                                                                                    • No—Exits the configuration session without committing the configuration changes.
                                                                                                    • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                     

                                                                                                    Configuring RPKI Cache-server

                                                                                                    Perform this task to configure Resource Public Key Infrastructure (RPKI) cache-server parameters.

                                                                                                    Configure the RPKI cache-server parameters in rpki-server configuration mode. Use the rpki server command in router BGP configuration mode to enter into the rpki-server configuration mode

                                                                                                    SUMMARY STEPS

                                                                                                      1.    configure

                                                                                                      2.    router bgp as-number

                                                                                                      3.    rpki cache {host-name | ip-address}

                                                                                                      4.    Use one of these commands:

                                                                                                      • transport ssh port port_number
                                                                                                      • transport tcp port port_number

                                                                                                      5.    (Optional) username user_name

                                                                                                      6.    (Optional) password

                                                                                                      7.    preference preference_value

                                                                                                      8.    purge-time time

                                                                                                      9.    Use one of these commands.

                                                                                                      • refresh-time time
                                                                                                      • refresh-time off

                                                                                                      10.    Use one these commands.

                                                                                                      • response-time time
                                                                                                      • response-time off

                                                                                                      11.    shutdown

                                                                                                      12.    Use the commit or end command.


                                                                                                    DETAILED STEPS
                                                                                                        Command or Action Purpose
                                                                                                      Step 1 configure


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router# configure
                                                                                                       

                                                                                                      Enters global configuration mode.

                                                                                                       
                                                                                                      Step 2 router bgp as-number


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config)#router bgp 100
                                                                                                       

                                                                                                      Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                                       
                                                                                                      Step 3 rpki cache {host-name | ip-address}


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp)#rpki server 10.2.3.4 
                                                                                                       

                                                                                                      Enters rpki-server configuration mode and enables configuration of RPKI cache parameters.

                                                                                                       
                                                                                                      Step 4 Use one of these commands:
                                                                                                      • transport ssh port port_number
                                                                                                      • transport tcp port port_number


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#transport ssh port 1

                                                                                                      Or

                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#transport tcp port 2
                                                                                                       
                                                                                                      Specifies a transport method for the RPKI cache.
                                                                                                      • ssh—Select ssh to connect to the RPKI cache using SSH.
                                                                                                      • tcp—Select tcp to connect to the RPKI cache using TCP (unencrypted).
                                                                                                      • port port_number—Specify a port number for the specified RPKI cache transport. Range for the port number is 1 to 65535 for both ssh and tcp.
                                                                                                      Note   

                                                                                                      You can set the transport to either TCP or SSH. Change of transport causes the cache session to flap.

                                                                                                       
                                                                                                      Step 5 username user_name


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#username ssh_rpki_cache
                                                                                                       
                                                                                                      (Optional)

                                                                                                      Specifies a (SSH) username for the RPKI cache-server.

                                                                                                       
                                                                                                      Step 6 password


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#password ssh_rpki_pass
                                                                                                       
                                                                                                      (Optional)

                                                                                                      Specifies a (SSH) password for the RPKI cache-server.

                                                                                                      Note   

                                                                                                      The “username” and “password” configurations only apply if the SSH method of transport is active.

                                                                                                       
                                                                                                      Step 7 preference preference_value


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#preference 1
                                                                                                       

                                                                                                      Specifies a preference value for the RPKI cache. Range for the preference value is 1 to 10. Setting a lower preference value is better.

                                                                                                       
                                                                                                      Step 8 purge-time time


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#purge-time 30
                                                                                                       

                                                                                                      Configures the time BGP waits to keep routes from a cache after the cache session drops. Set purge time in seconds. Range for the purge time is 30 to 360 seconds.

                                                                                                       
                                                                                                      Step 9 Use one of these commands.
                                                                                                      • refresh-time time
                                                                                                      • refresh-time off


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#refresh-time 20

                                                                                                      Or

                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#refresh-time off
                                                                                                       

                                                                                                      Configures the time BGP waits in between sending periodic serial queries to the cache. Set refresh-time in seconds. Range for the refresh time is 15 to 3600 seconds.

                                                                                                      Configure the off option to specify not to send serial-queries periodically.

                                                                                                       
                                                                                                      Step 10 Use one these commands.
                                                                                                      • response-time time
                                                                                                      • response-time off


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#response-time 30

                                                                                                      Or

                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#response-time off
                                                                                                       

                                                                                                      Configures the time BGP waits for a response after sending a serial or reset query. Set response-time in seconds. Range for the response time is 15 to 3600 seconds.

                                                                                                      Configure the off option to wait indefinitely for a response.

                                                                                                       
                                                                                                      Step 11 shutdown


                                                                                                      Example:
                                                                                                      RP/0/RSP0/CPU0:router(config-bgp-rpki-server)#shutdown
                                                                                                       

                                                                                                      Configures shut down of the RPKI cache.

                                                                                                       
                                                                                                      Step 12 Use the commit or end command.  

                                                                                                      commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                      end—Prompts user to take one of these actions:
                                                                                                      • Yes— Saves configuration changes and exits the configuration session.
                                                                                                      • No—Exits the configuration session without committing the configuration changes.
                                                                                                      • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                       

                                                                                                      Configuring RPKI Prefix Validation

                                                                                                      Perform this task to control the behavior of RPKI prefix validation processing.

                                                                                                      SUMMARY STEPS

                                                                                                        1.    configure

                                                                                                        2.    router bgp as-number

                                                                                                        3.    Use one of these commands.

                                                                                                        • rpki origin-as validation disable
                                                                                                        • rpki origin-as validation time {off | prefix_validation_time

                                                                                                        4.    origin-as validity signal ibgp

                                                                                                        5.    Use the commit or end command.


                                                                                                      DETAILED STEPS
                                                                                                          Command or Action Purpose
                                                                                                        Step 1 configure


                                                                                                        Example:
                                                                                                        RP/0/RSP0/CPU0:router# configure
                                                                                                         

                                                                                                        Enters global configuration mode.

                                                                                                         
                                                                                                        Step 2 router bgp as-number


                                                                                                        Example:
                                                                                                        RP/0/RSP0/CPU0:router(config)#router bgp 100
                                                                                                         

                                                                                                        Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                                         
                                                                                                        Step 3 Use one of these commands.
                                                                                                        • rpki origin-as validation disable
                                                                                                        • rpki origin-as validation time {off | prefix_validation_time


                                                                                                        Example:
                                                                                                        RP/0/RSP0/CPU0:router(config-bgp)#rpki origin-as validation disable

                                                                                                        Or

                                                                                                        RP/0/RSP0/CPU0:router(config-bgp)#rpki origin-as validation time 50

                                                                                                        Or

                                                                                                        RP/0/RSP0/CPU0:router(config-bgp)#rpki origin-as validation time off
                                                                                                         
                                                                                                        Sets the BGP origin-AS validation parameters.
                                                                                                        • disable—Use disable option to disable RPKI origin-AS validation.
                                                                                                        • time—Use time option to either set prefix validation time (in seconds) or to set off the automatic prefix validation after an RPKI update. Range for prefix validation time is 5 to 60 seconds. Configuring the disable option disables prefix validation for all eBGP paths and all eBGP paths are marked as "valid" by default.
                                                                                                          Note   

                                                                                                          The rpki origin-as validation options can also configured in neighbor and neighbor address family submodes. The neighbor must be an ebgp neighbor. If configured at the neighbor or neighor address family level, prefix validation disable or time options will be valid only for that specific neighbor or neighbor address family.

                                                                                                         
                                                                                                        Step 4 origin-as validity signal ibgp


                                                                                                        Example:
                                                                                                        RP/0/RSP0/CPU0:router(config-bgp)#rpki origin-as validity signal ibgp
                                                                                                         

                                                                                                        Enables the iBGP signaling of validity state through an extended-community.

                                                                                                        This can also be configured in global address family submode.

                                                                                                         
                                                                                                        Step 5 Use the commit or end command.  

                                                                                                        commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                        end—Prompts user to take one of these actions:
                                                                                                        • Yes— Saves configuration changes and exits the configuration session.
                                                                                                        • No—Exits the configuration session without committing the configuration changes.
                                                                                                        • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                         

                                                                                                        Configuring RPKI Bestpath Computation

                                                                                                        Perform this task to configure RPKI bestpath computation options.

                                                                                                        SUMMARY STEPS

                                                                                                          1.    configure

                                                                                                          2.    router bgp as-number

                                                                                                          3.    rpki bestpath use origin-as validity

                                                                                                          4.    rpki bestpath origin-as allow invalid

                                                                                                          5.    Use the commit or end command.


                                                                                                        DETAILED STEPS
                                                                                                            Command or Action Purpose
                                                                                                          Step 1 configure


                                                                                                          Example:
                                                                                                          RP/0/RSP0/CPU0:router# configure
                                                                                                           

                                                                                                          Enters global configuration mode.

                                                                                                           
                                                                                                          Step 2 router bgp as-number


                                                                                                          Example:
                                                                                                          RP/0/RSP0/CPU0:router(config)#router bgp 100
                                                                                                           

                                                                                                          Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

                                                                                                           
                                                                                                          Step 3 rpki bestpath use origin-as validity


                                                                                                          Example:
                                                                                                          RP/0/RSP0/CPU0:router(config-bgp)#rpki bestpath use origin-as validity
                                                                                                           

                                                                                                          Enables the validity states of BGP paths to affect the path's preference in the BGP bestpath process. This configuration can also be done in router BGP address family submode.

                                                                                                           
                                                                                                          Step 4 rpki bestpath origin-as allow invalid


                                                                                                          Example:
                                                                                                          RP/0/RSP0/CPU0:router(config-bgp)#rpki bestpath origin-as allow invalid
                                                                                                           
                                                                                                          Allows all "invalid" paths to be considered for BGP bestpath computation.
                                                                                                          Note   

                                                                                                          This configuration can also be done at global address family, neighbor, and neighbor address family submodes. Configuring rpki bestpath origin-as allow invalid in router BGP and address family submodes allow all "invalid" paths to be considered for BGP bestpath computation. By default, all such paths are not bestpath candidates. Configuring pki bestpath origin-as allow invalid in neighbor and neighbor address family submodes allow all "invalid" paths from that specific neighbor or neighbor address family to be considered as bestpath candidates. The neighbor must be an eBGP neighbor.

                                                                                                          This configuration takes effect only when the rpki bestpath use origin-as validity configuration is enabled.

                                                                                                           
                                                                                                          Step 5 Use the commit or end command.  

                                                                                                          commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                          end—Prompts user to take one of these actions:
                                                                                                          • Yes— Saves configuration changes and exits the configuration session.
                                                                                                          • No—Exits the configuration session without committing the configuration changes.
                                                                                                          • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                           

                                                                                                          Configuring VRF Dynamic Route Leaking

                                                                                                          Perform these steps to import routes from default-VRF to non-default VRF or to import routes from non-default VRF to default VRF.

                                                                                                          Before You Begin

                                                                                                          A route-policy is mandatory for configuring dynamic route leaking. Use the route-policy route-policy-name command in global configuration mode to configure a route-policy.

                                                                                                          SUMMARY STEPS

                                                                                                            1.    configure

                                                                                                            2.    vrf vrf_name

                                                                                                            3.    address-family {ipv4 | ipv6} unicast

                                                                                                            4.    Use one of these options:

                                                                                                            • import from default-vrf route-policy route-policy-name [advertise-as-vpn]
                                                                                                            • export to default-vrf route-policy route-policy-name

                                                                                                            5.    Use the commit or end command.


                                                                                                          DETAILED STEPS
                                                                                                              Command or Action Purpose
                                                                                                            Step 1 configure


                                                                                                            Example:
                                                                                                            RP/0/RSP0/CPU0:router# configure
                                                                                                             

                                                                                                            Enters global configuration mode.

                                                                                                             
                                                                                                            Step 2 vrf vrf_name


                                                                                                            Example:
                                                                                                            RP/0/RSP0/CPU0:PE51_ASR-9010(config)#vrf vrf_1
                                                                                                             

                                                                                                            Enters VRF configuration mode.

                                                                                                             
                                                                                                            Step 3 address-family {ipv4 | ipv6} unicast


                                                                                                            Example:
                                                                                                            RP/0/RSP0/CPU0:router(config-vrf)#address-family ipv6 unicast
                                                                                                             

                                                                                                            Enters VRF address-family configuration mode.

                                                                                                             
                                                                                                            Step 4 Use one of these options:
                                                                                                            • import from default-vrf route-policy route-policy-name [advertise-as-vpn]
                                                                                                            • export to default-vrf route-policy route-policy-name


                                                                                                            Example:
                                                                                                            RP/0/RSP0/CPU0:router(config-vrf-af)#import from default-vrf route-policy rpl_dynamic_route_import

                                                                                                            or

                                                                                                            RP/0/RSP0/CPU0:router(config-vrf-af)#export to default-vrf route-policy rpl_dynamic_route_export
                                                                                                            
                                                                                                             
                                                                                                            Imports routes from default-VRF to non-default VRF or from non-default VRF to default-VRF.
                                                                                                            • import from default-vrf—configures import from default-VRF to non-default-VRF. If the advertise-as-vpn option is configured, the paths imported from the default-VRF to the non-default-VRF are advertised to the PEs as well as to the CEs. If the advertise-as-vpn option is not configured, the paths imported from the default-VRF to the non-default-VRF are not advertised to the PE. However, the paths are still advertised to the CEs.
                                                                                                            • export to default-vrf—configures import from non-default-VRF to default VRF. The paths imported from the default-VRF are advertised to other PEs.
                                                                                                             
                                                                                                            Step 5 Use the commit or end command.  

                                                                                                            commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                            end—Prompts user to take one of these actions:
                                                                                                            • Yes— Saves configuration changes and exits the configuration session.
                                                                                                            • No—Exits the configuration session without committing the configuration changes.
                                                                                                            • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                             
                                                                                                            What to Do Next

                                                                                                            These show bgp command output displays information from the dynamic route leaking configuration:

                                                                                                            • Use the show bgp prefix command to display the source-RD and the source-VRF for imported paths, including the cases when IPv4 or IPv6 unicast prefixes have imported paths.
                                                                                                            • Use the show bgp imported-routes command to display IPv4 unicast and IPv6 unicast address-families under the default-VRF.

                                                                                                            Enabling Selective VRF Download

                                                                                                            To enable selective VRF download, configure the svd platform enable command followed by router reload.

                                                                                                            Note


                                                                                                            Selective VRF download is disabled by default.


                                                                                                            SUMMARY STEPS

                                                                                                              1.    admin

                                                                                                              2.    configure

                                                                                                              3.    svd platform enable

                                                                                                              4.    Use the commit or end command.

                                                                                                              5.    show svd state

                                                                                                              6.    admin

                                                                                                              7.    reload location all

                                                                                                              8.    exit

                                                                                                              9.    show svd role


                                                                                                            DETAILED STEPS
                                                                                                                Command or Action Purpose
                                                                                                              Step 1 admin


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router# admin 
                                                                                                               

                                                                                                              Enters administration EXEC mode.

                                                                                                               
                                                                                                              Step 2 configure


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router(admin)#configure
                                                                                                               

                                                                                                              Enters Administrative configuration mode.

                                                                                                               
                                                                                                              Step 3 svd platform enable


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router(admin-config)#svd platform enable
                                                                                                               

                                                                                                              Enables selective VRF download.

                                                                                                               
                                                                                                              Step 4 Use the commit or end command.  

                                                                                                              commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                              end—Prompts user to take one of these actions:
                                                                                                              • Yes— Saves configuration changes and exits the configuration session.
                                                                                                              • No—Exits the configuration session without committing the configuration changes.
                                                                                                              • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                               
                                                                                                              Step 5 show svd state


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router#show svd state
                                                                                                              Selective VRF Download (SVD) Feature State:
                                                                                                              SVD Configuration State        Enabled
                                                                                                              SVD Operational State          Enabled
                                                                                                               

                                                                                                              Displays Selective VRF download feature state information.

                                                                                                               
                                                                                                              Step 6 admin


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router#admin
                                                                                                               

                                                                                                              Enters administrator mode.

                                                                                                               
                                                                                                              Step 7 reload location all


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router(admin)#reload loc all
                                                                                                              Tue Feb 12 07:51:25.279 UTC
                                                                                                              
                                                                                                              Preparing system for backup. This may take a few minutes especially for large
                                                                                                              configurations.
                                                                                                                      Status report: node0_RSP0_CPU0: START TO BACKUP
                                                                                                                      Status report: node0_RSP0_CPU0: BACKUP HAS COMPLETED SUCCESSFULLY
                                                                                                              [Done]
                                                                                                              Proceed with reload? [confirm]RP/0/RSP0/CPU0::This node received reload
                                                                                                               

                                                                                                              Reloads the chassis.

                                                                                                               
                                                                                                              Step 8 exit


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router(admin)#exit
                                                                                                               

                                                                                                              Exits administrator mode and enters EXEC mode.

                                                                                                               
                                                                                                              Step 9 show svd role


                                                                                                              Example:
                                                                                                              RP/0/RSP0/CPU0:router#show svd role
                                                                                                              Tue Feb 12 07:50:26.908 UTC
                                                                                                              
                                                                                                              Codes: (C) : user Configured role
                                                                                                              Node Name       IPv4 Role                 IPv6 Role
                                                                                                              --------------------------------------------------------------------
                                                                                                              0/RSP0/CPU0     Standard                  Standard
                                                                                                              0/0/CPU0        Customer Facing           Not Interested
                                                                                                              0/1/CPU0        Customer Facing           Not Interested
                                                                                                               

                                                                                                              Verifies if selective VRF download is active by confirming that svd roles are "customer facing" for the line cards that have VRF interfaces on them.

                                                                                                               
                                                                                                              What to Do Next

                                                                                                              After enabling SVD using the svd platform enable command, do not use the selective-vrf-download disable to turn off SVD.

                                                                                                              Disabling Selective VRF Download

                                                                                                              Selective VRF Download is disabled by default. However, if the SVD is enabled, perform these tasks to disable the functionality.

                                                                                                              SUMMARY STEPS

                                                                                                                1.    admin

                                                                                                                2.    configure

                                                                                                                3.    no svd platform enable

                                                                                                                4.    Use the commit or end command.

                                                                                                                5.    show svd state

                                                                                                                6.    admin

                                                                                                                7.    reload location all

                                                                                                                8.    exit

                                                                                                                9.    show svd role


                                                                                                              DETAILED STEPS
                                                                                                                  Command or Action Purpose
                                                                                                                Step 1 admin


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router# admin 
                                                                                                                 

                                                                                                                Enters administration EXEC mode.

                                                                                                                 
                                                                                                                Step 2 configure


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router(admin)#configure
                                                                                                                 

                                                                                                                Enters Administrative configuration mode.

                                                                                                                 
                                                                                                                Step 3 no svd platform enable


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:PE51_ASR-9010(admin-config)#no svd platform enable
                                                                                                                 

                                                                                                                Disables Selective VRF Download.

                                                                                                                 
                                                                                                                Step 4 Use the commit or end command.  

                                                                                                                commit—Saves the configuration changes, and remains within the configuration session.

                                                                                                                end—Prompts user to take one of these actions:
                                                                                                                • Yes— Saves configuration changes and exits the configuration session.
                                                                                                                • No—Exits the configuration session without committing the configuration changes.
                                                                                                                • Cancel—Remains in the configuration mode, without committing the configuration changes.
                                                                                                                 
                                                                                                                Step 5 show svd state


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router#show svd state
                                                                                                                Selective VRF Download (SVD) Feature State:
                                                                                                                SVD Configuration State        Unsupported
                                                                                                                SVD Operational State          Unsupported
                                                                                                                 

                                                                                                                Displays Selective VRF download feature state information.

                                                                                                                 
                                                                                                                Step 6 admin


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router#admin
                                                                                                                 

                                                                                                                Enters administrator mode.

                                                                                                                 
                                                                                                                Step 7 reload location all


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router(admin)#reload loc all
                                                                                                                Tue Feb 12 07:51:25.279 UTC
                                                                                                                
                                                                                                                Preparing system for backup. This may take a few minutes especially for large
                                                                                                                configurations.
                                                                                                                        Status report: node0_RSP0_CPU0: START TO BACKUP
                                                                                                                        Status report: node0_RSP0_CPU0: BACKUP HAS COMPLETED SUCCESSFULLY
                                                                                                                [Done]
                                                                                                                Proceed with reload? [confirm]RP/0/RSP0/CPU0::This node received reload
                                                                                                                 

                                                                                                                Reloads the chassis.

                                                                                                                 
                                                                                                                Step 8 exit


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router(admin)#exit
                                                                                                                 

                                                                                                                Exits administrator mode and enters EXEC mode.

                                                                                                                 
                                                                                                                Step 9 show svd role


                                                                                                                Example:
                                                                                                                RP/0/RSP0/CPU0:router#show svd role
                                                                                                                
                                                                                                                Codes: (C) : user Configured role
                                                                                                                Node Name       IPv4 Role                 IPv6 Role
                                                                                                                --------------------------------------------------------------------
                                                                                                                0/RSP0/CPU0     Standard                  Standard
                                                                                                                0/0/CPU0        Standard                  Standard
                                                                                                                0/1/CPU0        Standard                  Standard
                                                                                                                 

                                                                                                                Verifies if selective VRF download is inactive by confirming that svd roles are "standard" for the line cards that have VRF interfaces on them.

                                                                                                                 

                                                                                                                Configuration Examples for Implementing BGP

                                                                                                                This section provides the following configuration examples:

                                                                                                                Enabling BGP: Example

                                                                                                                The following shows how to enable BGP.

                                                                                                                  prefix-set static
                                                                                                                     2020::/64,
                                                                                                                     2012::/64,
                                                                                                                     10.10.0.0/16,
                                                                                                                     10.2.0.0/24
                                                                                                                  end-set
                                                                                                                  
                                                                                                                  route-policy pass-all
                                                                                                                    pass
                                                                                                                  end-policy
                                                                                                                  route-policy set_next_hop_agg_v4
                                                                                                                    set next-hop 10.0.0.1  
                                                                                                                  end-policy
                                                                                                                  
                                                                                                                  route-policy set_next_hop_static_v4
                                                                                                                    if (destination in static) then
                                                                                                                      set next-hop 10.1.0.1
                                                                                                                    else
                                                                                                                      drop
                                                                                                                    endif
                                                                                                                  end-policy
                                                                                                                  
                                                                                                                  route-policy set_next_hop_agg_v6
                                                                                                                    set next-hop 2003::121
                                                                                                                  end-policy
                                                                                                                  
                                                                                                                  route-policy set_next_hop_static_v6
                                                                                                                    if (destination in static) then
                                                                                                                       set next-hop 2011::121
                                                                                                                    else
                                                                                                                       drop
                                                                                                                    endif
                                                                                                                  end-policy
                                                                                                                  
                                                                                                                  router bgp 65000
                                                                                                                    bgp fast-external-fallover disable
                                                                                                                    bgp confederation peers
                                                                                                                      65001
                                                                                                                      65002
                                                                                                                    bgp confederation identifier 1
                                                                                                                    bgp router-id 1.1.1.1
                                                                                                                    address-family ipv4 unicast
                                                                                                                      aggregate-address 10.2.0.0/24 route-policy set_next_hop_agg_v4
                                                                                                                      aggregate-address 10.3.0.0/24 
                                                                                                                      redistribute static route-policy set_next_hop_static_v4
                                                                                                                    address-family ipv4 multicast
                                                                                                                      aggregate-address 10.2.0.0/24 route-policy set_next_hop_agg_v4
                                                                                                                      aggregate-address 10.3.0.0/24
                                                                                                                      redistribute static route-policy set_next_hop_static_v4
                                                                                                                    address-family ipv6 unicast
                                                                                                                      aggregate-address 2012::/64 route-policy set_next_hop_agg_v6
                                                                                                                      aggregate-address 2013::/64
                                                                                                                      redistribute static route-policy set_next_hop_static_v6
                                                                                                                    address-family ipv6 multicast
                                                                                                                      aggregate-address 2012::/64 route-policy set_next_hop_agg_v6
                                                                                                                      aggregate-address 2013::/64
                                                                                                                      redistribute static route-policy set_next_hop_static_v6
                                                                                                                    neighbor 10.0.101.60
                                                                                                                      remote-as 65000
                                                                                                                      address-family ipv4 unicast
                                                                                                                      address-family ipv4 multicast
                                                                                                                    neighbor 10.0.101.61
                                                                                                                      remote-as 65000 
                                                                                                                      address-family ipv4 unicast
                                                                                                                      address-family ipv4 multicast
                                                                                                                    neighbor 10.0.101.62
                                                                                                                      remote-as 3
                                                                                                                      address-family ipv4 unicast
                                                                                                                        route-policy pass-all in
                                                                                                                        route-policy pass-all out
                                                                                                                      address-family ipv4 multicast
                                                                                                                        route-policy pass-all in
                                                                                                                        route-policy pass-all out
                                                                                                                    neighbor 10.0.101.64
                                                                                                                      remote-as 5
                                                                                                                      update-source Loopback0
                                                                                                                      address-family ipv4 unicast
                                                                                                                        route-policy pass-all in
                                                                                                                        route-policy pass-all out
                                                                                                                      address-family ipv4 multicast
                                                                                                                        route-policy pass-all in
                                                                                                                        route-policy pass-all out
                                                                                                                  

                                                                                                                Displaying BGP Update Groups: Example

                                                                                                                The following is sample output from the show bgp update-group command run in EXEC configuration mode:

                                                                                                                  
                                                                                                                 show bgp update-group
                                                                                                                  
                                                                                                                  Update group for IPv4 Unicast, index 0.1:
                                                                                                                    Attributes:
                                                                                                                      Outbound Route map:rm
                                                                                                                      Minimum advertisement interval:30
                                                                                                                    Messages formatted:2, replicated:2
                                                                                                                    Neighbors in this update group:
                                                                                                                      10.0.101.92
                                                                                                                  
                                                                                                                  Update group for IPv4 Unicast, index 0.2:
                                                                                                                    Attributes:
                                                                                                                      Minimum advertisement interval:30
                                                                                                                    Messages formatted:2, replicated:2
                                                                                                                    Neighbors in this update group:
                                                                                                                      10.0.101.91
                                                                                                                  

                                                                                                                BGP Neighbor Configuration: Example

                                                                                                                The following example shows how BGP neighbors on an autonomous system are configured to share information. In the example, a BGP router is assigned to autonomous system 109, and two networks are listed as originating in the autonomous system. Then the addresses of three remote routers (and their autonomous systems) are listed. The router being configured shares information about networks 172 .16 .0.0 and 192.168 .7.0 with the neighbor routers. The first router listed is in a different autonomous system; the second neighbor and remote-as commands specify an internal neighbor (with the same autonomous system number) at address 172 .26 .234.2; and the third neighbor and remote-as commands specify a neighbor on a different autonomous system.

                                                                                                                  route-policy pass-all 
                                                                                                                   pass
                                                                                                                  end-policy
                                                                                                                  router bgp 109
                                                                                                                   address-family ipv4 unicast
                                                                                                                    network 172
                                                                                                                .16
                                                                                                                .0.0 255.255
                                                                                                                .0.0
                                                                                                                    network 192.168
                                                                                                                .7.0 255.255
                                                                                                                .0.0
                                                                                                                    neighbor 172
                                                                                                                .16
                                                                                                                .200.1 
                                                                                                                     remote-as 167
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    route-policy pass-out out
                                                                                                                    neighbor 172
                                                                                                                .26
                                                                                                                .234.2 
                                                                                                                     remote-as 109
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 172
                                                                                                                .26
                                                                                                                .64.19 
                                                                                                                     remote-as 99
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    route-policy pass-all out
                                                                                                                  

                                                                                                                BGP Confederation: Example

                                                                                                                The following is a sample configuration that shows several peers in a confederation. The confederation consists of three internal autonomous systems with autonomous system numbers 6001, 6002, and 6003. To the BGP speakers outside the confederation, the confederation looks like a normal autonomous system with autonomous system number 666 (specified using the bgp confederation identifier command).

                                                                                                                In a BGP speaker in autonomous system 6001, the bgp confederation peers command marks the peers from autonomous systems 6002 and 6003 as special eBGP peers. Hence, peers 171.16 .232.55 and 171.16 .232.56 get the local preference, next hop, and MED unmodified in the updates. The router at 171 .19 .69.1 is a normal eBGP speaker, and the updates received by it from this peer are just like a normal eBGP update from a peer in autonomous system 666.

                                                                                                                  router bgp 6001
                                                                                                                   bgp confederation identifier 666
                                                                                                                   bgp confederation peers 
                                                                                                                    6002
                                                                                                                    6003
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171.16
                                                                                                                .232.55 
                                                                                                                    remote-as 6002
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171.16
                                                                                                                .232.56 
                                                                                                                    remote-as 6003
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171
                                                                                                                .19
                                                                                                                .69.1 
                                                                                                                    remote-as 777
                                                                                                                  
                                                                                                                  

                                                                                                                In a BGP speaker in autonomous system 6002, the peers from autonomous systems 6001 and 6003 are configured as special eBGP peers. Peer 171 .17 .70.1 is a normal iBGP peer, and peer 199.99.99.2 is a normal eBGP peer from autonomous system 700.

                                                                                                                  router bgp 6002
                                                                                                                   bgp confederation identifier 666
                                                                                                                   bgp confederation peers 
                                                                                                                    6001
                                                                                                                    6003
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171
                                                                                                                .17
                                                                                                                .70.1 
                                                                                                                     remote-as 6002
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171.19
                                                                                                                .232.57 
                                                                                                                     remote-as 6001
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171.19
                                                                                                                .232.56 
                                                                                                                     remote-as 6003
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171
                                                                                                                .19
                                                                                                                .99.2 
                                                                                                                     remote-as 700
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    route-policy pass-all out
                                                                                                                  
                                                                                                                  

                                                                                                                In a BGP speaker in autonomous system 6003, the peers from autonomous systems 6001 and 6002 are configured as special eBGP peers. Peer 192 .168 .200.200 is a normal eBGP peer from autonomous system 701.

                                                                                                                  router bgp 6003
                                                                                                                   bgp confederation identifier 666
                                                                                                                   bgp confederation peers
                                                                                                                    6001
                                                                                                                    6002
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171.19
                                                                                                                .232.57 
                                                                                                                     remote-as 6001
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 171.19
                                                                                                                .232.55 
                                                                                                                     remote-as 6002
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 192
                                                                                                                .168
                                                                                                                .200.200 
                                                                                                                     remote-as 701
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    route-policy pass-all out
                                                                                                                  
                                                                                                                  

                                                                                                                The following is a part of the configuration from the BGP speaker 192 .168 .200.205 from autonomous system 701 in the same example. Neighbor 171.16 .232.56 is configured as a normal eBGP speaker from autonomous system 666. The internal division of the autonomous system into multiple autonomous systems is not known to the peers external to the confederation.

                                                                                                                  router bgp 701
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 172
                                                                                                                .16
                                                                                                                .232.56 
                                                                                                                     remote-as 666
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    route-policy pass-all out
                                                                                                                     exit
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 192
                                                                                                                .168
                                                                                                                .200.205 
                                                                                                                     remote-as 701
                                                                                                                  

                                                                                                                BGP Route Reflector: Example

                                                                                                                The following example shows how to use an address family to configure internal BGP peer 10.1.1.1 as a route reflector client for both unicast and multicast prefixes:

                                                                                                                  router bgp 140
                                                                                                                   address-family ipv4 unicast
                                                                                                                    neighbor 10.1.1.1
                                                                                                                     remote-as 140
                                                                                                                     address-family ipv4 unicast
                                                                                                                      route-reflector-client
                                                                                                                      exit
                                                                                                                     address-family ipv4 multicast
                                                                                                                      route-reflector-client
                                                                                                                  
                                                                                                                  

                                                                                                                BGP Nonstop Routing Configuration: Example

                                                                                                                The following example shows how to enable BGP NSR:

                                                                                                                 configure
                                                                                                                 router bgp 120
                                                                                                                 nsr
                                                                                                                 end
                                                                                                                
                                                                                                                

                                                                                                                The following example shows how to disable BGP NSR:

                                                                                                                 configure
                                                                                                                 router bgp 120
                                                                                                                 no nsr
                                                                                                                 end
                                                                                                                

                                                                                                                Primary Backup Path Installation: Example

                                                                                                                The following example shows how to enable installation of primary backup path:

                                                                                                                  router bgp 120
                                                                                                                 address-family ipv4 unicast
                                                                                                                  additional-paths receive
                                                                                                                  additional-paths send
                                                                                                                  additional-paths selection route-policy bgp_add_path
                                                                                                                 !
                                                                                                                !
                                                                                                                end
                                                                                                                  

                                                                                                                Allocated Local Label Retention: Example

                                                                                                                The following example shows how to retain the previously allocated local label for the primary path on the primary PE for 10 minutes after reconvergence:

                                                                                                                  router bgp 100
                                                                                                                  address-family l2vpn vpls-vpws
                                                                                                                    retain local-label 10
                                                                                                                  end
                                                                                                                  

                                                                                                                iBGP Multipath Loadsharing Configuration: Example

                                                                                                                The following is a sample configuration where 30 paths are used for loadsharing:

                                                                                                                router bgp 100
                                                                                                                 address-family ipv4 multicast
                                                                                                                  maximum-paths ibgp 30
                                                                                                                 !
                                                                                                                !
                                                                                                                end
                                                                                                                
                                                                                                                

                                                                                                                Originating Prefixes With AiGP: Example

                                                                                                                The following is a sample configuration for originating prefixes with the AiGP metric attribute:

                                                                                                                route-policy aigp-policy
                                                                                                                  set aigp-metric 4
                                                                                                                  set aigp-metric igp-cost
                                                                                                                end-policy
                                                                                                                !
                                                                                                                router bgp 100
                                                                                                                 address-family ipv4 unicast
                                                                                                                  network 10.2.3.4/24 route-policy aigp-policy
                                                                                                                  redistribute ospf osp1 metric 4 route-policy aigp-policy
                                                                                                                 !
                                                                                                                !
                                                                                                                end
                                                                                                                
                                                                                                                

                                                                                                                BGP Accept Own Configuration: Example

                                                                                                                This example shows how to configure BGP Accept Own on a PE router.
                                                                                                                router bgp 100
                                                                                                                 neighbor 45.1.1.1
                                                                                                                   remote-as 100
                                                                                                                   update-source Loopback0
                                                                                                                   address-family vpnv4 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    accept-own
                                                                                                                    route-policy drop_111.x.x.x out
                                                                                                                   !
                                                                                                                   address-family vpnv6 unicast
                                                                                                                    route-policy pass-all in
                                                                                                                    accept-own
                                                                                                                    route-policy drop_111.x.x.x out
                                                                                                                   !
                                                                                                                  !
                                                                                                                This example shows an InterAS-RR configuration for BGP Accept Own.
                                                                                                                router bgp 100
                                                                                                                 neighbor 45.1.1.1
                                                                                                                  remote-as 100
                                                                                                                  update-source Loopback0
                                                                                                                  address-family vpnv4 unicast
                                                                                                                   route-policy rt_stitch1 in
                                                                                                                   route-reflector-client
                                                                                                                   route-policy add_bgp_ao out
                                                                                                                  !
                                                                                                                  address-family vpnv6 unicast
                                                                                                                   route-policy rt_stitch1 in
                                                                                                                   route-reflector-client
                                                                                                                   route-policy add_bgp_ao out
                                                                                                                  !
                                                                                                                 !
                                                                                                                extcommunity-set rt cs_100:1
                                                                                                                  100:1
                                                                                                                end-set
                                                                                                                !
                                                                                                                extcommunity-set rt cs_1001:1
                                                                                                                  1001:1
                                                                                                                end-set
                                                                                                                !
                                                                                                                route-policy rt_stitch1
                                                                                                                  if extcommunity rt matches-any cs_100:1 then
                                                                                                                    set extcommunity rt cs_1000:1 additive
                                                                                                                 endif
                                                                                                                end-policy
                                                                                                                !
                                                                                                                route-policy add_bgp_ao
                                                                                                                  set community (accept-own) additive
                                                                                                                end-policy
                                                                                                                !
                                                                                                                

                                                                                                                BGP Unequal Cost Recursive Load Balancing: Example

                                                                                                                This is a sample configuration for unequal cost recursive load balancing:

                                                                                                                
                                                                                                                interface Loopback0
                                                                                                                 ipv4 address 20.20.20.20 255.255.255.255
                                                                                                                !
                                                                                                                interface MgmtEth0/RSP0/CPU0/0
                                                                                                                 ipv4 address 8.43.0.10 255.255.255.0
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/0
                                                                                                                 bandwidth 8000000 
                                                                                                                 ipv4 address 11.11.11.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:1::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/1
                                                                                                                 bandwidth 7000000
                                                                                                                 ipv4 address 11.11.12.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:2::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/2
                                                                                                                 bandwidth 6000000
                                                                                                                 ipv4 address 11.11.13.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:3::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/3
                                                                                                                 bandwidth 5000000
                                                                                                                 ipv4 address 11.11.14.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:4::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/4
                                                                                                                 bandwidth 4000000
                                                                                                                 ipv4 address 11.11.15.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:5::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/5
                                                                                                                 bandwidth 3000000
                                                                                                                 ipv4 address 11.11.16.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:6::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/6
                                                                                                                 bandwidth 2000000
                                                                                                                 ipv4 address 11.11.17.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:7::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/3/0/7
                                                                                                                 bandwidth 1000000
                                                                                                                 ipv4 address 11.11.18.11 255.255.255.0
                                                                                                                 ipv6 address 11:11:0:8::11/64
                                                                                                                !
                                                                                                                interface TenGigE0/4/0/0
                                                                                                                 description CONNECTED TO IXIA 1/3
                                                                                                                 transceiver permit pid all
                                                                                                                !
                                                                                                                interface TenGigE0/4/0/2
                                                                                                                 ipv4 address 9.9.9.9 255.255.0.0
                                                                                                                 ipv6 address 9:9::9/64
                                                                                                                 ipv6 enable
                                                                                                                !
                                                                                                                route-policy pass-all
                                                                                                                  pass
                                                                                                                end-policy
                                                                                                                !
                                                                                                                router static
                                                                                                                 address-family ipv4 unicast
                                                                                                                  202.153.144.0/24 8.43.0.1
                                                                                                                 !
                                                                                                                !
                                                                                                                router bgp 100
                                                                                                                 bgp router-id 20.20.20.20
                                                                                                                 address-family ipv4 unicast
                                                                                                                  maximum-paths eibgp 8
                                                                                                                  redistribute connected
                                                                                                                 !
                                                                                                                 neighbor 11.11.11.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth    
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.12.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.13.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.14.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.15.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.16.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.17.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                 neighbor 11.11.18.12
                                                                                                                  remote-as 200
                                                                                                                  dmz-link-bandwidth
                                                                                                                  address-family ipv4 unicast
                                                                                                                   route-policy pass-all in
                                                                                                                   route-policy pass-all out
                                                                                                                  !
                                                                                                                 !
                                                                                                                !
                                                                                                                end
                                                                                                                

                                                                                                                VRF Dynamic Route Leaking Configuration: Example

                                                                                                                These examples show how to configure VRF dynamic route leaking:

                                                                                                                Import Routes from default-VRF to non-default-VRF

                                                                                                                vrf vrf_1
                                                                                                                 address-family ipv6 unicast
                                                                                                                  import from default-vrf route-policy rpl_dynamic_route_import
                                                                                                                 !
                                                                                                                end
                                                                                                                

                                                                                                                Import Routes from non-default-VRF to default-VRF

                                                                                                                vrf vrf_1
                                                                                                                 address-family ipv6 unicast
                                                                                                                    export to default-vrf route-policy rpl_dynamic_route_export
                                                                                                                 !
                                                                                                                end
                                                                                                                

                                                                                                                Where to Go Next

                                                                                                                For detailed information about BGP commands, see Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference

                                                                                                                Additional References

                                                                                                                The following sections provide references related to implementing BGP.

                                                                                                                Related Documents

                                                                                                                Related Topic

                                                                                                                Document Title

                                                                                                                BGP commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

                                                                                                                Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference

                                                                                                                Cisco Express Forwarding (CEF) commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

                                                                                                                Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Command Reference

                                                                                                                MPLS VPN configuration information.

                                                                                                                Cisco ASR 9000 Series Aggregation Services Router MPLS Configuration Guide

                                                                                                                Bidirectional Forwarding Detection (BFD)

                                                                                                                Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Configuration Guide and Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Command Reference

                                                                                                                Task ID information.

                                                                                                                Configuring AAA Services on Cisco ASR 9000 Series Router module of Cisco ASR 9000 Series Aggregation Services Router System Security Configuration Guide

                                                                                                                Standards

                                                                                                                Standards

                                                                                                                Title

                                                                                                                draft-bonica-tcp-auth-05.txt

                                                                                                                Authentication for TCP-based Routing and Management Protocols, by R. Bonica, B. Weis, S. Viswanathan, A. Lange, O. Wheeler

                                                                                                                draft-ietf-idr-bgp4-26.txt

                                                                                                                A Border Gateway Protocol 4, by Y. Rekhter, T.Li, S. Hares

                                                                                                                draft-ietf-idr-bgp4-mib-15.txt

                                                                                                                Definitions of Managed Objects for the Fourth Version of Border Gateway Protocol (BGP-4), by J. Hass and S. Hares

                                                                                                                draft-ietf-idr-cease-subcode-05.txt

                                                                                                                Subcodes for BGP Cease Notification Message, by Enke Chen, V. Gillet

                                                                                                                draft-ietf-idr-avoid-transition-00.txt

                                                                                                                Avoid BGP Best Path Transitions from One External to Another, by Enke Chen, Srihari Sangli

                                                                                                                draft-ietf-idr-as4bytes-12.txt

                                                                                                                BGP Support for Four-octet AS Number Space, by Quaizar Vohra, Enke Chen

                                                                                                                MIBs

                                                                                                                MIBs

                                                                                                                MIBs Link

                                                                                                                To locate and download MIBs using Cisco IOS XR software, use the Cisco MIB Locator found at the following URL and choose a platform under the Cisco Access Products menu: http:/​/​cisco.com/​public/​sw-center/​netmgmt/​cmtk/​mibs.shtml

                                                                                                                RFCs

                                                                                                                RFCs

                                                                                                                Title

                                                                                                                RFC 1700

                                                                                                                Assigned Numbers

                                                                                                                RFC 1997

                                                                                                                BGP Communities Attribute

                                                                                                                RFC 2385

                                                                                                                Protection of BGP Sessions via the TCP MD5 Signature Option

                                                                                                                RFC 2439

                                                                                                                BGP Route Flap Damping

                                                                                                                RFC 2545

                                                                                                                Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing

                                                                                                                RFC 2796

                                                                                                                BGP Route Reflection - An Alternative to Full Mesh IBGP

                                                                                                                RFC 2858

                                                                                                                Multiprotocol Extensions for BGP-4

                                                                                                                RFC 2918

                                                                                                                Route Refresh Capability for BGP-4

                                                                                                                RFC 3065

                                                                                                                Autonomous System Confederations for BGP

                                                                                                                RFC 3392

                                                                                                                Capabilities Advertisement with BGP-4

                                                                                                                RFC 4271

                                                                                                                A Border Gateway Protocol 4 (BGP-4)

                                                                                                                RFC 4364

                                                                                                                BGP/MPLS IP Virtual Private Networks (VPNs)

                                                                                                                RFC 4724

                                                                                                                Graceful Restart Mechanism for BGP

                                                                                                                Technical Assistance

                                                                                                                Description

                                                                                                                Link

                                                                                                                The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

                                                                                                                http:/​/​www.cisco.com/​techsupport