Cisco Nexus 7000 Series NX-OS MPLS Configuration Guide

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Updated:
June 4, 2014

Chapter: InterAS Option B

InterAS Option B

This document explains the different InterAS option B configuration options. The available options are InterAS option B, InterAS option B (with RFC 3107), and InterAS option B lite. The limitations of InterAS option B lite are taken care of by the InterAS option B feature in the NX-OS 7.2(0)D1(1) version.

The InterAS option B (with RFC 3107) implementation ensures complete IGP isolation between the data centers and WAN. When BGP advertises a particular route to ASBR, it also distributes the label which is mapped to that route.

Note While the InterAS option B lite version is available in the 6.2(2) version, the InterAS option B and InterAS option B (with RFC 3107 implementation) options are available in the 7.2(0)D1(1) version.

This chapter includes the following sections:

Finding Feature Information

Your software release might not support all the features documented in this module. For the latest caveats and feature information, see the Bug Search Tool at https://tools.cisco.com/bugsearch/ and the release notes for your 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 “New and Changed Information” chapter or the Feature History table below.

Information About InterAS

An autonomous system (AS) is a single network or group of networks that is controlled by a common system administration group and using a single, clearly defined protocol. In many cases, virtual private networks (VPNs) extend to different ASes in different geographical areas. Some VPNs must extend across multiple service providers; these VPNs are called overlapping VPNs. The connection between ASes must be seamless to the customer, regardless of the complexity or location of the VPNs.

InterAS and ASBRs

Separate ASes from different service providers can communicate by exchanging information in the form of VPN IP addresses. The ASBRs use EBGP to exchange that information. The IBGP distributes the network layer information for IP prefixes throughout each VPN and each AS. The following protocols are used for sharing routing information:

  • Within an AS, routing information is shared using IBGP.
  • Between ASes, routing information is shared using EBGP. EBGP allows service providers to set up an interdomain routing system that guarantees loop-free exchange of routing information between separate ASes.

The primary function of EBGP is to exchange network reachability information between ASes, including information about the list of AS routes. The ASes use EBGP border edge routers to distribute the routes, which includes label-switching information. Each border edge router rewrites the next-hop and MPLS labels.

InterAS configuration supported in this MPLS VPN can include an interprovider VPN, which is MPLS VPNs that include two or more ASes, connected by separate border edge routers. The ASes exchange routes use EBGP, and no IBGP or routing information is exchanged between the ASes.

Exchanging VPN Routing Information

ASes exchange VPN routing information (routes and labels) to establish connections. To control connections between ASes, the PE routers and EBGP border edge routers maintain a label forwarding information base (LFIB). The LFIB manages the labels and routes that the PE routers and EBGP border edge routers receive during the exchange of VPN information.

The ASes use the following guidelines to exchange VPN routing information:

  • Routing information includes:

– The destination network.

– The next-hop field associated with the distributing router.

– A local MPLS label.

  • A route distinguisher (RD1) is part of a destination network address. It makes the VPN IP route globally unique in the VPN service provider environment.

The ASBRs are configured to change the next-hop when sending VPN NLRIs to the IBGP neighbors. Therefore, the ASBRs must allocate a new label when they forward the NLRI to the IBGP neighbors.

Packet Forwarding

 

The above figure shows how packets are forwarded between ASes in an interprovider network. A single EBGP connection is established between ASBRs and the ASBRs will exchange routes associated with all local VRFs.

Packets are sent between the ASBRs through MPLS. Packets use the routing information stored in the LFIB of each ASBR.

A data packet carries two levels of labels when it traverses between the ASBR:

  • The first label (IGP/Core label) directs the packet to the correct ASBR.
  • The second label (VPN route label) directs the packet to the appropriate VRF.

InterAS Options

Nexus 7000/7700 series switches support the following InterAS options:

  • InterAS option A - In an interAS option A network, autonomous system border router (ASBR) peers are connected by multiple subinterfaces with at least one interface VPN that spans the two ASes. These ASBRs associate each subinterface with a VPN routing and forwarding (VRF) instance and a BGP session to signal unlabeled IP prefixes. As a result, traffic between the back-to-back VRFs is IP. In this scenario, the VPNs are isolated from each other and, because the traffic is IP Quality of Service (QoS) mechanisms that operate on the IP traffic can be maintained. The downside of this configuration is that one BGP session is required for each subinterface (and at least one subinterface is required for each VPN), which causes scalability concerns as the network grows.
  • InterAS option B - In an interAS option B network, ASBR ports are connected by one or more subinterfaces that are enabled to receive MPLS traffic. A Multiprotocol Border Gateway Router (MP-BGP) session distributes labeled VPN prefixes between the ASBRs. As a result, the traffic that flows between the ASBRs is labeled. The downside of this configuration is that, because the traffic is MPLS, QoS mechanisms that are applied only to IP traffic cannot be carried and the VRFs cannot be isolated. InterAS option B provides better scalability than option A because it requires only one BGP session to exchange all VPN prefixes between the ASBRs. Also, this feature provides nonstop forwarding (NSF) and Graceful Restart. The ASBRs must be directly connected in this option.

Some functions of option B are noted below:

– You can have an IBGP VPNv4/v6 session between Nexus 7000/7700 series switches within an AS and you can have an EBGP VPNv4/v6 session between data center edge routers and WAN routers.

– There is no requirement for a per VRF IBGP session between data center edge routers, like in the lite version.

– LDP distributes IGP labels between ASBRs.

  • InterAS option B (with BGP-3107 or RFC 3107 implementation) -

– You can have an IBGP VPNv4/v6 implementation between Nexus 7000/7700 series edge switches within an AS and you can have an EBGP VPNv4/v6 session between data center edge routers and WAN routers.

– BGP-3107 enables BGP packets to carry label information without using LDP between ASBRs.

– The label mapping information for a particular route is piggybacked in the same BGP update message that is used to distribute the route itself.

– When BGP is used to distribute a particular route, it also distributes an MPLS label which is mapped to that route. Many ISPs prefer this method of configuration since it ensures complete IGP isolation between the data centers.

  • InterAS option B lite – Support for the InterAS option B feature is restricted in the Cisco NX-OS 6.2(2) release. Details are noted in the Configuring InterAS Option B (lite version) section.

Licensing Requirements for InterAS Option B

The following table shows the licensing requirements for this feature:

 

Product
License Requirement

Cisco NX-OS

MPLS Layer 3 requires an MPLS license. For a complete explanation of the NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Guidelines and Limitations for Configuring InterAS Option B

The InterAS option B feature is not supported with BGP confederation AS.

Configuring InterAS Option B

Note The Option B implementation is applicable for the 7.2(0)D1(1) version.

 

Configuring the Switch for InterAS Option B

Configuring BGP for InterAS Option B

Configuring the Switch for InterAS Option B

You enable certain features on the switch to run InterAS option B.

Prerequisites

Ensure that you are in the correct VDC (or use the switchto vdc command). The install feature-set mpls command is available only in the default VDC, and you must enable it in default VDC.

Configure VRFs on the DC edge switches with following steps:

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

install feature-set mpls

 

Example:

switch(config)# install feature-set mpls

Installs the MPLS feature set in the default VDC.

Note You can only install and enable MPLS in the default VDC. Use the no form of this command to uninstall the MPLS feature set.

Step 3

feature mpls ldp

 

Example:

switch(config)# feature mpls ldp

Enables the MPLS LDP feature on the device.

Note When the MPLS LDP feature is disabled on the device, no LDP commands are available.

Step 4

feature mpls l3vpn

 

Example:

switch(config)# feature mpls l3vpn

Enables the MPLS Layer 3 VPN feature.

Step 5

feature bgp

 

Example:

switch(config)# feature bgp

Enables the BGP feature.

Step 6

vrf-context vrf-name

 

Example:

switch(config)# vrf context VPN1

Defines the VPN routing instance by assigning a VRF name and enters VRF configuration mode.

The vrf-name argument is any case-sensitive, alphanumeric string up to 32 characters.

Step 7

rd route-target-ext-community

 

Example:

switch(config-vrf)# rd100:1

 

Configures the route distinguisher. The route-distinguisher argument adds an 8-byte value to an IPv4 prefix to create a VPN IPv4 prefix.

Step 8

address-family {ipv4 | ipv6} unicast

 

Example:

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

 

Specifies the IPv4 or IPv6 address family type and enters address family configuration mode.

Step 9

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

 

Example:

switch(config-vrf-af-ip4)# route-target import 1:1

 

Specifies a route-target extended community for a VRF as follows:

  • The import keyword imports routing information from the target VPN extended community.
  • The export keyword exports routing information to the target VPN extended community.
  • The route-target-ext-community argument adds the route-target extended community attributes to the VRF's list of import or export route-target extended communities.

Step 10

copy running-config startup-config

 

Example:

switch(config-vrf-af-ip4)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Configuring BGP for InterAS Option B

To configure BGP for InterAS option B, you need to enable this configuration on both the IBGP and EBGP sides. Refer to Figure 1 for reference.

Configure DC Edge switches with IBGP & EBGP VPNv4/v6 with the following steps:

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

switch(config)#

Enters global configuration mode.

Step 2

router bgp as-number

 

Example:

switch(config)# router bgp 100

 

Enters the router BGP configuration mode and assigns an autonomous system (AS) number to the local BGP speaker device.

Step 3

neighbor ip-address

 

Example:

switch(config-router)# neighbor 10.0.0.2

 

Adds an entry to the BGP or multiprotocol BGP neighbor table, and enters router BGP neighbor configuration mode.

Step 4

remote-as as-number

 

Example:

switch(config-router-neighbor)# remote-as 200

 

The as-number argument specifies the autonomous system to which the neighbor belongs.

Step 5

address-family {vpnv4 | vpnv6} unicast

 

Example:

switch(config-router-neighbor)# address-family vpnv4 unicast

 

Enters address family configuration mode for configuring IP VPN sessions.

Step 6

send-community {both | extended}

 

Example:

switch(config-router-neighbor-af)# send-community both

 

Specifies that a communities attribute should be sent to both BGP neighbors.

Step 7

retain route-target all

 

Example:

switch(config-router-neighbor-af)# retain route-target all

 

(Optional). Retains VPNv4/v6 address configuration on the ASBR without VRF configuration

Note If you have a VRF configuration on the ASBR, this command is not required.

Step 8

vrf vrf-name

 

Example:

switch(config-router-neighbor-af)# vrf VPN1

 

Associates the BGP process with a VRF.

Step 9

address-family {ipv4 | ipv6} unicast

 

Example:

switch(config-router-vrf)# address-family ipv4 unicast

 

Specifies the IPv4 or IPv6 address family and enters address family configuration mode.

Step 10

exit

 

Example:

switch(config-vrf-af)# exit

Exits IPv4 address family.

Step 11

copy running-config startup-config

Example:

switch(config-router-vrf)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Configuring InterAS Option B (with RFC 3107 implementation)

Note This implementation is the same as the option B implementation (explained in the previous task), except that BGP is used to advertise labels for loopbacks of ASBRs. In the option B (without RFC 3107) implementation, a tunnel label was advertised by IGP+LDP between ASBRs. Here, BGP is used to advertise the label and there is no need to run an IGP between the ASBRs.

Configuring the Switch for InterAS Option B (with RFC 3107 implementation)

Configuring BGP for InterAS Option B (with RFC 3107 implementation)

Creating an ACL to filter LDP connections between the ASBRs (RFC 3107 implementation)

Configuring the Switch for InterAS Option B (with RFC 3107 implementation)

Configure VRFs on the DC edge switches with following steps.

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

install feature-set mpls

 

Example:

switch(config)# install feature-set mpls

Installs the MPLS feature set in the default VDC.

Note You can only install and enable MPLS in the default VDC. Use the no form of this command to uninstall the MPLS feature set.

Step 3

feature mpls ldp

 

Example:

switch(config)# feature mpls ldp

Enables the MPLS LDP feature on the device.

Note When the MPLS LDP feature is disabled on the device, no LDP commands are available.

Step 4

feature mpls l3vpn

 

Example:

switch(config)# feature mpls l3vpn

Enables the MPLS Layer 3 VPN feature.

Step 5

feature bgp

 

Example:

switch(config)# feature bgp

Enables the BGP feature.

Step 6

vrf-context vrf-name

 

Example:

switch(config)# vrf context VPN1

Defines the VPN routing instance by assigning a VRF name and enters VRF configuration mode.

The vrf-name argument is any case-sensitive, alphanumeric string up to 32 characters.

Step 7

rd route-distinguisher

 

Example:

switch(config-vrf)# rd 100:1

Configures the route distinguisher. The route-distinguisher argument adds an 8-byte value to an IPv4 prefix to create a VPN IPv4 prefix.

Step 8

address-family {ipv4 | ipv6} unicast

 

Example:

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

 

Specifies the IPv4 or IPv6 address family type and enters address family configuration mode.

Step 9

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

 

Example:

switch(config-vrf-af-ip4)# route-target import 1:1

 

Specifies a route-target extended community for a VRF as follows:

  • The import keyword imports routing information from the target VPN extended community.
  • The export keyword exports routing information to the target VPN extended community.
  • The route-target-ext-community argument adds the route-target extended community attributes to the VRF's list of import or export route-target extended communities.

Step 10

copy running-config startup-config

 

Example:

switch(config-vrf-af-ip4)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Configuring BGP for InterAS Option B (with RFC 3107 implementation)

Configure DC Edge switches with IBGP & EBGP VPNv4/v6 along with BGP labeled unicast family with following steps:

Prerequisites

Ensure that you are in the correct VDC (or use the switchto vdc command).

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

router bgp as-number

 

Example:

switch(config)# router bgp 200

 

Enters the router BGP configuration mode and assigns an autonomous system (AS) number to the local BGP speaker device.

In this example, the ASBR and AS are ASBR2 and AS-200, respectively.

Step 3

address-family {ipv4 | ipv6} unicast

 

Example:

switch(config-router)# address-family ipv4 unicast

 

Enters address family configuration mode for configuring IPv4 or IPv6 sessions.

Step 4

redistribute direct route-map tag

 

Example:

switch(config-router-af)# redistribute direct route-map loopback

 

Redistributes directly connected routes using the Border Gateway Protocol.

Step 5

allocate-label all

Example:

switch(config-router-af)# allocate-label all

 

Configures ASBRs with the BGP labeled unicast address family to advertise labels for the connected interface.

Step 6

exit

Example:

switch(config-router-af)# exit

 

Exits address family router configuration mode and enters router BGP configuration mode.

Step 7

neighbor ip-address

 

Example:

switch(config-router)# neighbor 10.1.1.1

Configures the BGP neighbour’s IP address, and enters router BGP neighbour configuration mode.

Step 8

remote-as as-number

 

Example:

switch(config-router-neighbor)# remote-as 100

Specifies the BGP neighbour’s AS number.

Step 9

address-family {ipv4|ipv6} labeled-unicast 

 

Example:

switch(config-router-neighbor)# address-family ipv4 labeled-unicast

Configures the ASBR with the BGP labeled unicast address family to advertise labels for the connected interface.

Note This is the command that implements RFC 3107.

Step 10

retain route-target all

 

Example:

switch(config-router-neighbor-af)# retain route-target all

(Optional). Retains VPNv4/v6 address configuration on the ASBR without VRF configuration.

If you have a VRF configuration on the ASBR, this command is not required.

Step 11

exit

 

Example:

Switch(config-router-neighbor-af)# exit

Note Enter the exit command twice.

Exits router BGP neighbour address family configuration mode and returns to router BGP configuration mode.

Step 12

neighbor ip-address

 

Example:

switch(config-router)# neighbor 1.1.1.1

Configures a loopback IP address, and enters router BGP neighbor configuration mode.

Step 13

remote-as as-number

 

Example:

switch(config-router-neighbor)# remote-as 100

Specifies the BGP neighbour’s AS number.

Step 14

address-family {vpnv4|vpnv6} unicast 

 

Example:

switch(config-router-neighbor)# address-family vpnv4 unicast

Configures the ASBR with the BGP VPNv4 unicast address family.

Step 15

exit 

 

Example:

switch(config-router-neighbor-af)# exit

Enters router BGP neighbor configuration mode again.

Step 16

address-family {vpnv4|vpnv6} unicast 

 

Example:

switch(config-router-neighbor)# address-family vpnv6 unicast

Configures the ASBR with the BGP VPNv6 unicast address family.

Step 17

Repeat the process with ASBR2.

Configures ASBR2 with option B (RFC 3107) settings and implements complete IGP isolation between the two data centers DC1 and DC2.

Step 18

copy running-config startup-config  

 

Example:

switch(config-router-neighbor-af)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Creating an ACL to filter LDP connections between the ASBRs (RFC 3107 implementation)

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

ip access-list name

 

Example:

switch(config)# ip access-list LDP

 

Creates an access list and enters ACL configuration mode.

Step 3

[ sequence-number ] deny tcp any any eq packet-length

 

Example:

switch(config-acl)# 10 deny tcp any any eq 646

 

Executes the ACL instruction as per the specified sequence.

Step 4

[ sequence-number ] deny tcp any eq packet-length any

 

Example:

switch(config-acl)# 20 deny tcp any eq 646 any

 

Executes the ACL instruction as per the specified sequence.

Step 5

[ sequence-number ] deny udp any any eq packet-length

 

Example:

switch(config-acl)# 30 deny udp any any eq 646

 

Executes the ACL instruction as per the specified sequence.

Step 6

[ sequence-number ] deny udp any eq packet-length any

 

Example:

switch(config-acl)# 40 deny udp any eq 646 any

 

Executes the ACL instruction as per the specified sequence.

Step 7

[ sequence-number ] permit ip any any

 

Example:

switch(config-acl)# 50 permit ip any any

 

Executes the ACL instruction as per the specified sequence.

Step 8

exit

 

Example:

switch(config-acl)# exit

Exits ACL configuration mode and enters global configuration mode.

Step 9

interface type number 

 

Example:

switch(config)# interface ethernet 2/20

Enters interface configuration mode.

Step 10

mpls ip

 

Example:

switch(config-if)# mpls ip

Configures MPLS hop-by-hop forwarding on this interface.

Step 11

ip access-group name in

 

Example:

switch(config-if)# ip access-group LDP in

Specifies that the ACL (named LDP created in the earlier steps) be applied to inbound traffic on the interface.

Step 12

ip access-group name out

 

Example:

switch(config-if)# ip access-group LDP out

Specifies that the ACL (named LDP created in the earlier steps) be applied to the outbound traffic on the interface.

Step 13

end

 

Example:

switch(config-if)# end

Exits interface configuration mode and returns to the privileged EXEC mode.

Configuring InterAS Option B (lite Version)

Guidelines and Limitations for Configuring InterAS Option B lite [applicable to the 6.2(2) release version]

  • The aggregation switch supports only local VRFs, and Nexus devices within an autonomous system (AS) are connected through a VRF implementation.
  • Routes learned from the IBGP peer are not sent to the EBGP peer and routes learned from an EBGP peer are not sent to IBGP VPNv4/VPNv6 peers.
  • The interAS option B with MP-BGP on the EBGP side does not work with MP-BGP on the IBGP side. One interface goes to the core and one interface goes to the Layer 3 VPN.
  • MP-BGP Layer 3 VPN does not work within an AS.

 

This section contains information on the following topics:

Configuring the Switch for InterAS Option B (lite version)

You enable certain features on the switch to run interAS option B.

Prerequisites

Ensure that you are in the correct VDC (or use the switchto vdc command).

The install feature-set mpls command is available only in the default VDC, and you must enable it in default VDC.

 

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

install feature-set mpls

 

Example:

switch(config)# install feature-set mpls

Installs the MPLS feature set in the default VDC.

Note You can only install and enable MPLS in the default VDC. Use the no form of this command to uninstall the MPLS feature set.

Step 3

feature mpls ldp

 

Example:

switch(config)# feature mpls ldp

 

Enables the MPLS LDP feature on the device.

Note When the MPLS LDP feature is disabled on the device, no LDP commands are available.

Step 4

feature mpls l3vpn

 

Example:

switch(config)# feature mpls l3vpn

Enables the MPLS Layer 3 VPN feature.

Step 5

feature bgp

 

Example:

switch(config)# feature bgp

Enables the BGP feature.

Step 6

vrf-context vrf-name

 

Example:

switch(config)# vrf-context VPN1

 

Defines the VPN routing instance by assigning a VRF name and enters VRF configuration mode. The vrf-name argument is any case-sensitive, alphanumeric string up to 32 characters.

Step 7

rd route-distinguisher

 

Example:

switch(config-vrf)# rd 100:1

 

Configures the route distinguisher. The route-distinguisher argument adds an 8-byte value to an IPv4 prefix to create a VPN IPv4 prefix.

Step 8

address-family {ipv4 | ipv6} unicast

 

Example:

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

 

Specifies the IPv4 or IPv6 address family type and enters address family configuration mode.

Step 9

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

 

Example:

switch(config-vrf-af-ip4)# route-target import 1:1

 

Specifies a route-target extended community for a VRF as follows:

  • The import keyword imports routing information from the target VPN extended community.
  • The export keyword exports routing information to the target VPN extended community.
  • The route-target-ext-community argument adds the route-target extended community attributes to the VRF's list of import or export route-target extended communities.

Step 10

copy running-config startup-config

 

Example:

switch(config-vrf-af-ip4)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Configuring the Interfaces for InterAS Option B (lite Version)

Configure DC Edge switches with vrf-lite using the following steps.

Prerequisites

Ensure that you are in the correct VDC (or use the switchto vdc command).

 

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

interface type number

 

Example:

switch(config)# interface ethernet 2/1

 

Specifies the interface to configure and enters interface configuration mode.

Step 3

description description

 

Example:

switch(config-if)# description To other ASBR

 

Specifies a description for the interface.

Step 4

ip address prefix mask

 

Example:

switch(config-if)# ip address 10.0.0.1 255.255.255.0

 

Configures IP address for interface.

Step 5

no shutdown

 

Example:

switch(config-if)# no shutdown

 

Enables interface.

Step 6

exit

 

Example:

switch(config-if)# exit

 

Exits interface configuration mode and enters glbal configuration mode.

Step 7

interface type number

 

Example:

switch(config-if)# interface ethernet 2/2

 

Specifies the interface to configure and enters interface configuration mode.

Step 8

description description

 

Example:

switch(config-if)# description To CE

 

Specifies a description for the interface.

Step 9

vrf member vrf-name

 

Example:

switch(config-if)# vrf member VPN1

 

Associates a VRF with the specified interface or subinterface. The vrf-name argument is the name assigned to a VRF.

Step 10

ip address prefix mask

 

Example:

switch(config-if)# ip address 10.0.2.1 255.255.255.0

 

Configures an IP address for the interface.

Step 11

ipv6 address address

 

Example:

switch(config-if)# ipv6 address 2001:DB8:1::1

 

Configures an IPv6 address for interface.

Step 12

no shutdown

 

Example:

switch(config-if)# no shutdown

 

Enables the interface.

Step 13

copy running-config startup-config

 

Example:

switch(config-if)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Configuring BGP for InterAS Option B (lite Version)

Prerequisites

Ensure that you are in the correct VDC (or use the switchto vdc command).

Configure EBGP VPNv4/v6 on the DC Edge switches using the following steps:

DETAILED STEPS

 

Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

 

Enters global configuration mode.

Step 2

router bgp as-number

 

Example:

switch(config)# router bgp 100

 

Enters the router BGP configuration mode and assigns an autonomous system (AS) number to the local BGP speaker device.

Step 3

neighbor ip-address

 

Example:

switch(config-router)# neighbor 10.0.0.2

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

Step 4

remote-as as-number

 

Example:

switch(config-router-neighbor)# remote-as 200

 

The as-number argument specifies the autonomous system to which the neighbor belongs.

Step 5

address-family {vpnv4 | vpnv6} unicast

 

Example:

switch(config-router-neighbor)# address-family vpnv4 unicast

 

Enters address family configuration mode for configuring IP VPN sessions.

Step 6

send-community {both | extended}

 

Example:

switch(config-router-neighbor-af)# send-community both

 

Specifies that a communities attribute should be sent to both BGP neighbors.

Step 7

vrf vrf-name

 

Example:

switch(config-router-neighbor-af)# vrf VPN1

 

Associates the BGP process with a VRF.

Step 8

address-family {ipv4 | ipv6} unicast

 

Example:

switch(config-router-vrf)# address-family ipv4 unicast

 

Enters address family configuration mode for configuring IP VPN sessions.

Step 9

exit

 

Example:

switch(config-router-vrf-af)# exit

 

Exits IPv4 address family.

Step 10

copy running-config startup-config

 

Example:

switch(config-router-vrf)# copy running-config startup-config

(Optional) Copies the running configuration to the startup configuration.

Verifying InterAS Option B Configuration

To verify InterAS option B configuration information, perform one of the following tasks:

Command
Purpose

show bgp { vpnv4 | vpnv6 } unicast [ ip-prefix/length [ neighbors neighbor ] ] { vrf { vrf-name | all } | rd route-distinguisher }

Displays VPN routes from the BGP table.

show bgp ipv6 unicast [ vrf vrf-name ]

Displays information about BGP on a VRF for 6VPE.

show forwarding { ip | ipv6 } route vrf vrf-name

Displays the IP forwarding table that is associated with a VRF. Check that the loopback addresses of the local and remote CE routers are in the routing table of the PE routers.

show { ip | ipv6 } bgp [ vrf vrf-name ]

Displays information about BGP on a VRF.

show ip route [ ip-address [ mask ]] [ protocol ] vrf vrf-name

Displays the current state of the routing table. Use the ip-address argument to verify that CE1 has a route to CE2. Verify the routes learned by CE1. Make sure that the route for CE2 is listed.

show { ip | ipv6 } route vrf vrf-name

Displays the IP routing table that is associated with a VRF. Check that the loopback addresses of the local and remote CE routers are in the routing table of the PE routers.

show running-config bgp

Displays the running configuration for BGP.

show running-config vrf vrf-name

Displays the running configuration for VRFs.

show vrf vrf-name interface if-type

Verifies the route distinguisher (RD) and interface that are configured for the VRF.

trace destination [ vrf vrf-name ]

Discovers the routes that packets take when traveling to their destination. The trace command can help isolate a problem if two routers cannot communicate.

Configuration Examples for Configuring InterAS Option B

Example: Configuring InterAS Option B

!--Configure VRFs on the DC edge switches --!
 
configure terminal
install feature-set mpls
feature mpls ldp
feature mpls l3vpn
feature bgp
vrf context VPN1
rd 100:1
address-family ipv4 unicast
route-target import 1:1
copy running-config startup-config
 
!--Configure DC Edge switches with IBGP & EBGP VPNv4/v6 --!
 
configure terminal
router bgp 100
neighbor 10.0.0.2
remote-as 200
address-family vpnv4 unicast
send-community both
retain route-target all
vrf VPN1
address-family ipv4 unicast
exit
copy running-config startup-config

Example: Configuring InterAS Option B (RFC 3107)

!--Configure VRFs on the DC edge switches --!
 
configure terminal
install feature-set mpls
feature mpls ldp
feature mpls l3vpn
feature bgp
vrf context VPN1
rd 100:1
address-family ipv4 unicast
route-target import 1:1
copy running-config startup-config
 
!--Configure DC Edge switches with IBGP & EBGP VPNv4/v6 --!
 
configure terminal
router bgp 100
address-family ipv4 unicast
redistribute direct route-map loopback
allocate-label all
exit
neighbor 10.1.1.1
remote-as 100
address-family ipv4 labeled-unicast
retain route-target all
exit
neighbor 1.1.1.1
remote-as 100
address-family vpnv4 unicast
address-family vpnv6 unicast
!--Repeat the process with ASBR2. --!
copy running-config startup-config
 
!--Creating an ACL to filter LDP connection between the ASBRs (RFC 3107 implementation)--!
 
configure terminal
ip access-list LDP
10 deny tcp any any eq 646
20 deny tcp any eq 646 any
30 deny udp any any eq 646
40 deny udp any eq 646 any
50 permit ip any any
exit
interface ethernet 2/20
mpls ip
ip access-group LDP in
ip access-group LDP out
end

Additional References for Configuring InterAS Option B

This section includes the following topics:

Related Documents

Related Topic
Document Title

CLI commands

Cisco Nexus 7000 Series NX-OS MPLS Command Reference

Interface commands

Cisco Nexus 7000 Series NX-OS Interface Command Reference

VRF-aware services

Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide

MIBs

MIBs
MIBs Link
  • MPLS-L3VPN-STD-MIB

To locate and download MIBs, go to the following URL: http://www.cisco.com/dc-os/mibs

Feature History for Configuring InterAS Option B

Table 26-1 lists the release history for this feature.

Table 26-1 Feature History for InterAS Option B

Feature Name
Releases
Feature Information

InterAS option B

7.2(0)D1(1)

This feature was enhanced with the InterAS option B and InterAS option B (with RFC 3107) provisions. An IBGP VPNv4/v6 session between DC edge routers and an EBGP VPNv4/v6 session between DC edge routers and WAN routers can be established without a per VRF iBGP session between DC edge routers.

The InterAS option B (with RFC 3107) implementation ensures complete IGP isolation between the data centers and WAN.

InterAS option B lite

6.2(2)

This feature was introduced as a lite version.

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