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Table Of Contents

BGP Event-Based VPN Import

Finding Feature Information

Contents

Prerequisites for BGP Event-Based VPN Import

Information About BGP Event-Based VPN Import

BGP Event-Based VPN Import

Import Path Selection Policy

Import Path Limit

How to Configure BGP Event-Based VPN Import

Configuring a Multiprotocol VRF

Configuring Event-Based VPN Import Processing for BGP Paths

Prerequisites

Monitoring and Troubleshooting BGP Event-Based VPN Import Processing

Configuration Examples for BGP Event-Based VPN Import

Configuring Event-Based VPN Import Processing for BGP Paths: Example

Where to Go Next

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for BGP Event-Based VPN Import


BGP Event-Based VPN Import

First Published: October 2, 2009
Last Updated: September 10, 2010

The BGP Event-Based VPN Import feature introduces a modification to the existing Border Gateway Protocol (BGP) path import process. The enhanced BGP path import is driven by events; when a BGP path changes, all of its imported copies are updated as soon as processing is available. Convergence times are significantly reduced because there is no longer any delay in the propagation of routes due to the software waiting for a periodic scanner time interval before processing the updates. To implement the new processing, new command-line interface (CLI) commands are introduced.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for BGP Event-Based VPN Import" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for BGP Event-Based VPN Import

•Information About BGP Event-Based VPN Import

•How to Configure BGP Event-Based VPN Import

•Configuration Examples for BGP Event-Based VPN Import

•Additional References

•Feature Information for BGP Event-Based VPN Import

Prerequisites for BGP Event-Based VPN Import

Cisco Express Forwarding or distributed Cisco Express Forwarding must be enabled on all participating routers.

Information About BGP Event-Based VPN Import

•BGP Event-Based VPN Import

BGP Event-Based VPN Import

The BGP Event-Based VPN Import feature introduces a modification to the existing BGP path import process. BGP Virtual Private Network (VPN) import provides importing functionality for BGP paths where BGP paths are imported from the BGP VPN table into a BGP virtual routing and forwarding (VRF) topology. In the existing path import process, when path updates occur, the import updates are processed during the next scan time which is a configurable interval of 5 to 15 seconds. The scan time adds a delay in the propagation of routes. The enhanced BGP path import is driven by events; when a BGP path changes, all of its imported copies are updated as soon as processing is available.

Using the BGP Event-Based VPN Import feature, convergence times are significantly reduced because provider edge (PE) routers can propagate VPN paths to customer edge (CE) routers without the scan time delay. Configuration changes such as adding imported route-targets to a VRF are not processed immediately, and are still handled during the 60-second periodic scanner pass.

Import Path Selection Policy

Event-based VPN import introduces three path selection policies:

•All—Import all available paths from the exporting net that match any Route Target (RT) associated with the importing VRF instance.

•Bestpath—Import the best available path that matches the RT of the VRF instance. If the bestpath in the exporting net does not match the RT of the VRF instance, a best available path that matches the RT of the VRF instance is imported.

•Multipath—Import the bestpath and all paths marked as multipaths that match the RT of the VRF instance. If there are no bestpath or multipath matches, then the best available path is selected.

Multipath and bestpath options can be restricted using an optional keyword to ensure that the selection is made only on the configured option. If the strict keyword is configured, the software disables the fall back safety option of choosing the best available path. If there are no paths appropriate to the configured option (bestpath or multipath) in the exporting net that match the RT of the VRF instance, then no paths are imported. This behavior matches the behavior of the software before the BGP Event-Based VPN Import feature was introduced.

When the restriction is not set, paths that are imported as the best available path are tagged. In show command output these paths are identified with the wording, "imported safety path."

The paths existing in an exporting net that are considered for import into a VRF instance may have been received from another peer router and were not subject to the VPN importing rules. These paths may contain the same route-distinguisher (RD) information because the RD information is local to a router, but some of these paths do not match the RT of the importing VRF instance and are marked as "not-in-vrf" in the show command output. Any path that is marked as "not-in-vrf" is not considered as a bestpath because paths not in the VRF appear less attractive than paths in the VRF.

Import Path Limit

To control the memory utilization, a maximum limit of the number of paths imported from an exporting net can be specified per importing net. When a selection is made of paths to be imported from one or more exporting net, the first selection priority is a bestpath, the next selection priority is for multipaths, and the lowest selection priority is for nonmultipaths.

How to Configure BGP Event-Based VPN Import

•Configuring a Multiprotocol VRF

•Configuring Event-Based VPN Import Processing for BGP Paths

•Monitoring and Troubleshooting BGP Event-Based VPN Import Processing

Configuring a Multiprotocol VRF

Perform this task to configure a multiprotocol VRF that allows you to share route-target policies (import and export) between IPv4 and IPv6 or to configure separate route-target policies for IPv4 and IPv6 VPNs. In this task, only the IPv4 address family is configured, but we recommend using the multiprotocol VRF configuration for all new VRF configurations.

Note This task is not specific to the BGP Event-Based VPN Import feature.

SUMMARY STEPS

1. enable

2. configure terminal

3. vrf definition vrf-name

4. rd route-distinguisher

5. route-target {import | export | both} route-target-ext-community

6. address-family ipv4 [unicast]

7. exit-address-family

8. exit

9. interface type number

10. vrf forwarding vrf-name

11. ip address ip-address mask

12. no shutdown

13. exit

14. Repeat Step 3 through Step 13 to create and bind other VRF instances with an interface.

15. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

vrf definition vrf-name

Example:

Router(config)# vrf definition vrf-A

Configures a VRF routing table and enters VRF configuration mode.

•Use the vrf-name argument to specify a name to be assigned to the VRF.

Step 4 

rd route-distinguisher

Example:

Router(config-vrf)# rd 45000:1

Creates routing and forwarding tables and specifies the default route distinguisher for a VPN.

•Use the route-distinguisher argument to add an 8-byte value to an IPv4 prefix to create a unique VPN IPv4 prefix.

Step 5 

route-target {import | export | both} route-target-ext-community

Example:

Router(config-vrf)# route-target both 45000:100

Creates a route target extended community for a VRF.

•Use the import keyword to import routing information from the target VPN extended community.

•Use the export keyword to export routing information to the target VPN extended community.

•Use the both keyword to both import routing information from, and export routing information to, the target VPN extended community.

•Use the route-target-ext-community argument to add the route target extended community attributes to the VRF's list of import, export, or both (import and export) route target extended communities.

Step 6 

address-family ipv4 [unicast]

Example:

Router(config-vrf)# address-family ipv4 unicast

Specifies the IPv4 address family and enters VRF address family configuration mode.

•This step is required here to specify an address family for the VRF defined in the previous steps.

Step 7 

exit-address-family

Example:

Router(config-vrf-af)# exit-address-family

Exits VRF address family configuration mode and returns to VRF configuration mode.

Step 8 

exit

Example:

Router(config-vrf)# exit

Exits VRF configuration mode and enters global configuration mode.

Step 9 

interface type number

Example:

Router(config)# interface FastEthernet 1/1

Enters interface configuration mode.

Step 10 

vrf forwarding vrf-name

Example:

Router(config-if)# vrf forwarding vrf-A

Associates a VRF instance with the interface configured in Step 9.

•When the interface is bound to a VRF, previously configured IP addresses are removed, and the interface is disabled.

Step 11 

ip address ip-address mask

Example:

Router(config-if)# ip address 10.4.8.149 255.255.255.0

Configures an IP address for the interface.

Step 12 

no shutdown

Example:

Router(config-if)# no shutdown

Restarts a disabled interface.

Step 13 

exit

Example:

Router(config-if)# exit

Exits interface configuration mode and enters global configuration mode.

Step 14 

Repeat Step 3 through Step 13 to bind other VRF instances with an interface.

—

Step 15 

end

Example:

Router(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Configuring Event-Based VPN Import Processing for BGP Paths

Perform this task to reduce convergence times when BGP paths change by configuring event-based processing for importing BGP paths into a VRF table. Two new CLI commands allow the configuration of a maximum number of import paths per importing net and the configuration of a path selection policy.

Prerequisites

This task assumes that you have previously configured the VRF to be used with the VRF address family syntax. To configure a VRF, see the "Configuring a Multiprotocol VRF" section.

Complete BGP neighbor configuration is also assumed. For an example configuration, see the "Configuring Event-Based VPN Import Processing for BGP Paths: Example" section.

SUMMARY STEPS

1. enable

2. configure terminal

3. router bgp autonomous-system-number

4. address-family ipv4 vrf vrf-name

5. import path selection {all | bestpath [strict] | multipath [strict]}

6. import path limit number-of-import-paths

7. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

router bgp autonomous-system-number

Example:

Router(config)# router bgp 45000

Enters router configuration mode for the specified routing process.

Step 4 

address-family ipv4 vrf vrf-name

Example:

Router(config-router)# address-family ipv4 vrf vrf-A

Specifies the IPv4 address family and enters address family configuration mode.

•Use the vrf keyword and vrf-name argument to specify the name of the VRF instance to associate with subsequent IPv4 address family configuration mode commands.

Step 5 

import path selection {all | bestpath [strict] | multipath [strict]}

Example:

Router(config-router-af)# import path selection all

Specifies the BGP path selection policy for importing routes into a VRF table.

•In this example, all paths that match any RT of the VRF instance are imported.

Step 6 

import path limit number-of-import-paths

Example:

Router(config-router-af)# import path limit 3

Specifies, per importing net, a maximum number of BGP paths that can be imported from an exporting net.

Step 7 

end

Example:

Router(config-router-af)# end

Exits address family configuration mode and returns to privileged EXEC mode.

Monitoring and Troubleshooting BGP Event-Based VPN Import Processing

Perform the steps in this task as required to monitor and troubleshoot the BGP event-based VPN import processing.

Only partial command syntax for the show commands used in this task is displayed. For more details, see the Cisco IOS IP Routing: BGP Command Reference.

SUMMARY STEPS

1. enable

2. show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [network-address [mask]]

3. show ip route [vrf vrf-name] [ip-address [mask]]

4. debug ip bgp import {events | updates [access-list | expanded-access-list]}

DETAILED STEPS

Step 1 enable

Enables privileged EXEC mode. Enter your password if prompted. 

Router> enable

Step 2 show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [network-address [mask]]

In this example output, a safe import path selection policy is in effect because the strict keyword is not configured using the import path selection command. When a path is imported as the best available path (when the bestpath or multipaths are not eligible for import), the path is marked with "imported safety path," as shown in the output. 

Router# show ip bgp vpnv4 all 172.17.0.0


BGP routing table entry for 45000:1:172.17.0.0/16, version 10

Paths: (1 available, best #1, table vrf-A)

Flag: 0x820

   Not advertised to any peer

   2, imported safety path from 50000:2:172.17.0.0/16

     10.0.101.1 from 10.0.101.1 (10.0.101.1)

       Origin IGP, metric 200, localpref 100, valid, internal, best

       Extended Community: RT:45000:100

The paths existing in an exporting net that are considered for import into a VRF instance may have been received from another peer router and were not subject to the VPN importing rules. These paths may contain the same route-distinguisher (RD) information because the RD information is local to a router, but some of these paths do not match the RT of the importing VRF instance and are marked as "not-in-vrf" in the show command output.

In the following example output, a path was received from another peer router and was not subject to the VPN importing rules. This path, 10.0.101.2, was added to the VPNv4 table and associated with the vrf-A net because it contains a match of the RD information although the RD information was from the original router. This path is not, however, an RT match for vrf-A and is marked as "not-in-vrf." Note that on the net for vrf-A, this path is not the bestpath because any paths that are not in the VRF appear less attractive than paths in the VRF. 

Router# show ip bgp vpnv4 all 172.17.0.0


BBGP routing table entry for 45000:1:172.17.0.0/16, version 11

Paths: (2 available, best #2, table vrf-A)

Flag: 0x820

   Not advertised to any peer

   2

     10.0.101.2 from 10.0.101.2 (10.0.101.2)

       Origin IGP, metric 100, localpref 100, valid, internal, not-in-vrf

       Extended Community: RT:45000:200

       mpls labels in/out nolabel/16

   2

     10.0.101.1 from 10.0.101.1 (10.0.101.1)

       Origin IGP, metric 50, localpref 100, valid, internal, best

       Extended Community: RT:45000:100

       mpls labels in/out nolabel/16

Step 3 show ip route [vrf vrf-name] [ip-address [mask]]

In this example output, information about the routing table for VRF vrf-A is displayed: 

Router# show ip route vrf vrf-A 172.17.0.0


Routing Table: vrf-A

Routing entry for 172.17.0.0/16

  Known via "bgp 1", distance 200, metric 50

  Tag 2, type internal

  Last update from 10.0.101.33 00:00:32 ago

  Routing Descriptor Blocks:

  * 10.0.101.33 (default), from 10.0.101.33, 00:00:32 ago

      Route metric is 50, traffic share count is 1

      AS Hops 1

      Route tag 2

      MPLS label: 16

      MPLS Flags: MPLS Required

Step 4 debug ip bgp vpnv4 unicast import {events | updates [access-list]}

Use this command to display debugging information related to the importing of BGP paths into a VRF instance table. The actual output depends on the commands that are subsequently entered.

Note If no access list to filter prefixes is specified when using the updates keyword, all updates for all prefixes are displayed and this may slow down your network. 

Router# debug ip bgp vpnv4 unicast import events


BGP import events debugging is on

Configuration Examples for BGP Event-Based VPN Import

•Configuring Event-Based VPN Import Processing for BGP Paths: Example

Configuring Event-Based VPN Import Processing for BGP Paths: Example

In this example configuration, a VRF (vrf-A) is configured and VRF forwarding is applied to Fast Ethernet interface 1/1. In address family mode the import path selection is set to all and the number of import paths is set to 3. Two BGP neighbors are configured under the IPv4 address family and activated under the VPNv4 address family. 

vrf definition vrf-A

 rd 45000:1

 route-target import 45000:100

 address-family ipv4

  exit-address-family

!

interface FastEthernet1/1

 no ip address

 vrf forwarding vrf-A

 ip address 10.4.8.149 255.255.255.0

 no shut

 exit

!

router bgp 45000

 network 172.17.1.0 mask 255.255.255.0

 neighbor 192.168.1.2 remote-as 40000

 neighbor 192.168.3.2 remote-as 50000

 address-family ipv4 vrf vrf-A

  import path selection all

  import path limit 3

  exit-address-family

 address-family vpnv4

  neighbor 192.168.1.2 activate

  neighbor 192.168.3.2 activate

  end

Where to Go Next

•If you want to connect to an external service provider and use other external BGP features, see the "Connecting to a Service Provider Using External BGP" module.

•If you want to configure some internal BGP features, see the "Configuring Internal BGP Features" chapter of the BGP section of the Cisco IOS IP Routing Protocols Configuration Guide.

•If you want to configure BGP neighbor session options, see the "Configuring BGP Neighbor Session Options" module.

•If you want to configure some advanced BGP features, see the "Configuring Advanced BGP Features" module.

Additional References

The following sections provide references related to the BGP Event-Based VPN Import feature.

Related Documents

Related Topic
Document Title

BGP commands: complete command syntax, command mode, defaults, command history, usage guidelines, and examples

Cisco IOS IP Routing: BGP Command Reference

Overview of Cisco BGP conceptual information with links to all the individual BGP modules

"Cisco BGP Overview" module of the Cisco IOS IP Routing: BGP Configuration Guide.

Conceptual and configuration details for basic BGP tasks.

"Configuring a Basic BGP Network" module of the Cisco IOS IP Routing Protocols Configuration Guide.

Command Lookup Tool

http://tools.cisco.com/Support/CLILookup

Cisco IOS Master Command List

http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html


Standards

Standard
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—


MIBs

MIB
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs


RFCs

RFC
Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—


Technical Assistance

Description
Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport


Feature Information for BGP Event-Based VPN Import

Table 1 lists the release history for this feature.

Table 1 lists the features in this module and provides links to specific configuration information. Only features that were introduced or modified in Cisco IOS Releases 15.0(1)M, 12.2(33)SRE, or a later release appear in the table.

For information on a feature in this technology that is not documented here, see the "Cisco BGP Implementation Roadmap."

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for BGP Event-Based VPN Import 

Feature Name
Releases
Feature Information

BGP Event-Based VPN Import

12.2(33)SRE
15.0(1)M
15.0(1)S
Cisco IOS XE 3.1.0SG

The BGP Event-Based VPN Import feature introduces a modification to the existing Border Gateway Protocol (BGP) path import process. The enhanced BGP path import is driven by events; when a BGP path changes, all of its imported copies are updated as soon as processing is available. Convergence times are significantly reduced because there is no longer any delay in the propagation of routes due to the software waiting for a periodic scanner time interval before processing the updates. To implement the new processing, new command-line interface (CLI) commands are introduced.

The following commands were introduced or modified: bgp scan-time, import path limit, import path selection, maximum-path ebgp, maximum-path ibgp, show ip bgp vpnv4, show ip bgp vpnv6.


Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2010 Cisco Systems, Inc. All rights reserved.