BGP—IPv6 NSR

Border Gateway Protocol (BGP) support for Nonstop Routing (NSR) enables provider edge (PE) routers to maintain BGP state with customer edge (CE) routers and ensure continuous packet forwarding during a Route Processor (RP) switchover or during a planned In-Service Software Upgrade (ISSU) for a PE router. The BGP—IPv6 NSR feature extends BGP support for NSR to Cisco IPv6 VPN Provider Edge Routers (6VPE).

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 table at the end of this module.

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

Prerequisites for BGP—IPv6 NSR

  • Your network is configured to run BGP.

  • Multiprotocol Layer Switching (MPLS) Layer 3 Virtual Private Networks (VPNs) are configured.

  • All platforms are HA capable.

  • You are familiar with the concepts in the “BGP Support for Nonstop Routing (NSR) with Stateful Switchover (SSO)” and “BGP NSR Support for iBGP Peers” modules of the IP Routing: BGP Configuration Guide.

Information About BGP—IPv6 NSR

Overview of BGP—IPv6 NSR

Nonstop routing (NSR) is beneficial for BGP peers because it reduces the likelihood of dropped packets during switchover from the active Route Processor (RP) to the standby RP. Switchover occurs when the active RP fails for some reason and the standby RP takes control of active RP operations. The BGP—IPv6 NSR feature extends BGP support for NSR to include the following IPv6-based address families:

  • IPv6 unicast

  • IPv6 unicast + label

  • IPv6 PE-CE

  • VPNv6 unicast

Figure 1. Basic 6VPE Network Configuration

The figure above depicts a basic deployment scenario. Provider edge (PE) router 1, P, and PE2 form a 6VPE cloud. The customer edge (CE) router 1 to PE1 connection is IPv6 (VRF). The PEs are HA/SSO and NSF capable. The P routers are capable of Multiprotocol Label Switching (MPLS) label preservation (NSF equivalent).

As the CE1 is customer equipment, the provider cannot determine that it must be upgraded to be NSF aware. If PE1 can perform NSR on its connection to CE1, then CE1 will not be aware or impacted when PE1 performs a switchover in SSO mode. For all other connections within the autonomous system, the operations may be NSF or graceful restart. This means the control plane will be reset, and all the immediate peers will be aware of it and will resend data to help re-establish the session, but forwarding will be uninterrupted.

Neighbors not operating under NSR are still expected to be NSF capable/aware. If the CE is already NSF aware (that is, it can handle a BGP graceful restart by its peers), then the PE-CE connection will not be NSR, and will instead follow the regular NSF processing model. This parallels NSR for VPNv4 and assists in conserving network resources.

How to Configure BGP—IPv6 NSR

Configuring BGP—IPv6 NSR

Perform this task on a PE router if you want to configure a BGP peer to support BGP—IPv6 NSR.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    router bgp autonomous-system-number

    4.    Enter one of the following:

    • address-family ipv6 [unicast | multicast | vpnv6] [vrf vrf-name]
    • address-family vpnv6 [unicast | multicast]

    5.    neighbor ipv6-address% remote-as as-number

    6.    neighbor ipv6-address% activate

    7.    neighbor ipv6-address% ha-mode sso

    8.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 router bgp autonomous-system-number


    Example:
    Device(config)# router bgp 4000
     

    Enters router configuration mode for the specified routing process.

     
    Step 4Enter one of the following:
    • address-family ipv6 [unicast | multicast | vpnv6] [vrf vrf-name]
    • address-family vpnv6 [unicast | multicast]


    Example:
    Device(config-router)# address-family ipv6 unicast
     

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

    • The unicast keyword specifies the IPv6 unicast address family.

    • The vrf keyword and vrf-name argument specify the name of the virtual routing and forwarding (VRF) instance to associate with subsequent IPv6 address family configuration mode commands.

     
    Step 5 neighbor ipv6-address% remote-as as-number


    Example:
    Device(config-router-af)# neighbor 2001:DB8:0:CC00::1 remote-as 4000
     

    Specifies the autonomous system of the neighbor.

     
    Step 6 neighbor ipv6-address% activate


    Example:
    Device(config-router-af)# neighbor 2001:DB8:0:CC00::1 activate
     

    Activates the specified peer.

     
    Step 7 neighbor ipv6-address% ha-mode sso


    Example:
    Device(config-router-af)# neighbor 2001:DB8:0:CC00::1 ha-mode sso
     

    Configures a BGP neighbor to support BGP NSR.

     
    Step 8 end


    Example:
    Device(config-router-af)# end
     

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

     

    Configuration Examples for BGP—IPv6 NSR

    Example: Configuring BGP—IPv6 NSR

    router bgp 4000
 address-family ipv6 unicast
 neighbor 2001:DB8:0:CC00::1 remote-as 4000
 neighbor 2001:DB8:0:CC00::1 activate
 neighbor 2001:DB8:0:CC00::1 ha-mode sso

    Additional References for BGP—IPv6 NSR

    Related Documents

    Related Topic Document Title

    Cisco IOS commands

    Cisco IOS Master Command List, All Releases

    BGP commands

    Cisco IOS IP Routing: BGP Command Reference

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    Feature Information for BGP—IPv6 NSR

    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
    Table 1 Feature Information for BGP—IPv6 NSR

    Feature Name

    Releases

    Feature Information

    BGP—IPv6 NSR

    Cisco IOS XE Release 3.9S

    BGP support for NSR enables provider edge (PE) routers to maintain BGP state with customer edge (CE) routers and ensure continuous packet forwarding during a Route Processor (RP) switchover or during a planned ISSU for a PE router. The BGP—IPv6 NSR feature extends BGP support for NSR to Cisco IPv6 VPN Provider Edge Routers (6VPE).