IP Routing: BGP Configuration Guide, Cisco IOS Release 15M&T
VRF Aware BGP Translate-Update
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VRF Aware BGP Translate-Update

VRF Aware BGP Translate-Update

The VRF aware BGP translate-update feature enables multicast forwarding on those customer-edge (CE) devices, which have an older version of Cisco software that does not support multicast BGP (mBGP) routing.

The provider-edge (PE) devices establish a virtual routing and forwarding (VRF) session with the neighbor CE devices, and configure the translate-update feature under an IPv4/IPv6 VRF address family. The PE devices translate the updates from unicast to multicast on CE devices and put them as multicast updates in the Border Gateway Protocol (BGP) VRF routing table of the PE devices for processing.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for VRF Aware BGP Translate-Update

  • The VRF aware translate-update feature applies only to IPv4/IPv6 virtual routing and forwarding (VRF) address-families.
  • You must use peer-group for the configuration of the neighbor under IPv4/IPv6 VRF address families.
  • BGP neighbors that are only capable of unicast routing, must be activated under both unicast and multicast address families.
  • BGP neighbors must also be enabled under the compatible multicast address family for the VRF aware translate-update feature to function as designed.
  • The provider-edge (PE) devices must have multicast VRF enabled and must have a session established with the customer-edge (CE) devices.

Restrictions for VRF Aware BGP Translate-Update

  • You must not configure (nonVRF) IPv4/IPv6 address families for the VRF aware BGP translate-update feature. The IPv4/IPv6 address family must be configured for multicast routing using the Subsequent Address Family Identifier (SAFI) feature.
  • The VRF aware BGP translate-update feature does not support configuration of BGP neighbor using peer-template.

Information About VRF Aware BGP Translate-Update

VRF Aware BGP Translate-Update Overview

The VRF aware BGP translate-update feature enables multicast forwarding on those customer-edge (CE) devices, which have an older version of Cisco software that does not support multicast BGP (mBGP) routing.

This feature is analogous to the Subsequent Address Family Identifier (SAFI), which provides the capability to support multicast routing in the service provider's core IPv4 network, but is limited in support to IPv4/IPv6 address families. In the case of the virtual routing and forwarding (VRF) aware BGP translate-update feature, provider-edge (PE) devices establish a VRF session with the neighbor CE devices, and have the translate-update feature configured under an IPv4/IPv6 VRF address family.

When the neighbor translate-update command is configured on a PE device under the (IPv4 VRF) address-family configuration mode or the (IPv6 VRF) address-family configuration mode, the PE devices translate the updates from unicast to multicast on CE devices and put them in the Border Gateway Protocol (BGP) VRF routing table of the PE devices, as multicast updates, for processing. If you also configure the optional keyword unicast, the updates that are not translated, are placed in the PE device's unicast queue and populates the unicast VRF BGP table. The translation from unicast to multicast routes occurs from CE devices to PE devices only, and the multicast and unicast prefixes are only advertised from the CE device to the PE device's multicast neighbors.

For example, when you configure the VRF aware BGP translate-update feature under a VRF (v1) for a neighbor CE device (CE1), a neighbor topology under the IPv4-multicast-VRF or IPv6-multicast-VRF address-family is added to CE1's session with a PE device (PE1). The multicast-VRF neighbor topology does not actively participate in these multicast sessions and only forwards announcements that arrive from CE1. Once such announcements arrive, they are translated into multicast and placed in the nonactive multicast VRF neighbor's routing table. The Cisco software ensures that the routes advertised by CE1 configured under the IPv4/IPv6 VRF address-family are available on PE1's IPv4/IPv6 multicast VRF v1 address-family BGP table. These routes, along with PE1's IPv4/IPv6 multicast VRF v1 address-family BGP table, are advertised to PE1's multicast peers if you have configured the neighbor translate-update command . The routes are also advertised to PE1's unicast peers if you have also configured the optional keyword unicast.

The unicast keyword is optional, yet significant, as it enables the PE devices to place unicast advertisements from the CE devices in the unicast BGP table of the PE devices. Therefore, route advertisements from CE devices populates both unicast and multicast BGP tables, else CE device's routes only populate the PE device's multicast BGP table.


Note


You must also enable address-family under the compatible multicast address-family for VRF aware BGP translate-update feature to function as designed.

How To Configure VRF Aware BGP Translate-Update

Configuring VRF Aware BGP Translate-Update

Perform this task to configure VRF aware BGP translate-update feature:

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    router bgp as-number

    4.    address-family ipv4 [mdt | tunnel | {multicast | unicast} [vrf vrf-name] | vrf vrf-name]

    5.    neighbor peer-group-name peer-group

    6.    neighbor {ipv4-addr | ipv6-addr | peer-group-name} remote-as autonomous-system-number

    7.    neighbor {ipv4-addr | ipv6-addr} peer-group peer-group-name

    8.    neighbor {ipv4-addr | ipv6-addr | peer-group-name} activate

    9.    neighbor {ipv4-address | ipv6-address} translate-update multicast [unicast]

    10.    end

    11.    show bgp vpnv4 multicast {all | vrf vrf-name | rd route-distinguisher}

    12.    show ip route multicast vrf vrf-name

    13.    show running-config


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 as-number


    Example:
    Device(config)# router bgp 65000
     

    Enters router configuration mode and creates a BGP routing process.

     
    Step 4 address-family ipv4 [mdt | tunnel | {multicast | unicast} [vrf vrf-name] | vrf vrf-name]


    Example:
    Device(config)# address-family ipv4 vrf v1
     

    Enters address family configuration mode to configure a routing session using standard IP Version 4 (IPv4) address prefixes.

     
    Step 5 neighbor peer-group-name peer-group


    Example:
    Device(config-af)# neighbor n2 peer-group
     

    Creates a BGP or multiprotocol BGP peer group.

     
    Step 6 neighbor {ipv4-addr | ipv6-addr | peer-group-name} remote-as autonomous-system-number


    Example:
    Device(config-af)# neighbor n2 remote-as 4
     

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

     
    Step 7 neighbor {ipv4-addr | ipv6-addr} peer-group peer-group-name


    Example:
    Device(config-af)# neighbor 10.1.1.1 peer-group n2
     

    Configures a BGP neighbor to be a member of a peer group.

     
    Step 8 neighbor {ipv4-addr | ipv6-addr | peer-group-name} activate


    Example:
    Device(config-af)# neighbor 10.1.1.1 activate
     

    Enables exchange of information with a BGP neighbor.

     
    Step 9neighbor {ipv4-address | ipv6-address} translate-update multicast [unicast]


    Example:
    Device(config-af)# neighbor 10.1.1.1 translate-update multicast unicast
     

    Enables multicast routing on devices, which are not capable of multicast BGP (mBGP) routing.

     
    Step 10 end


    Example:
    Device(config-af)# end
     

    Returns to privileged EXEC mode.

     
    Step 11show bgp vpnv4 multicast {all | vrf vrf-name | rd route-distinguisher}


    Example:
    Device# show bgp vpnv4 mul vrf v1 summary
    
     

    Displays Virtual Private Network Version 4 (VPNv4) multicast entries in a BGP table.

     
    Step 12show ip route multicast vrf vrf-name


    Example:
    Device# show ip route multicast vrf v1
    
     

    Displays the IP routing table associated with a specific multicast VPN routing and forwarding (VRF) instance.

     
    Step 13show running-config


    Example:
    Device# show running-config
    
     

    Displays the running configuration on the device.

     

    Removing the VRF Aware BGP Translate-Update Configuration

    Perform this task to disable the VRF aware BGP translate-update feature:

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    router bgp as-number

      4.    address-family ipv4 [mdt | tunnel | {multicast | unicast} [vrf vrf-name] | vrf vrf-name]

      5.    no neighbor {ipv4-address | ipv6-address} translate-update multicast [unicast]

      6.    end

      7.    show running-config


    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 as-number


      Example:
      Device(config)# router bgp 65000
       

      Enters router configuration mode and creates a BGP routing process.

       
      Step 4 address-family ipv4 [mdt | tunnel | {multicast | unicast} [vrf vrf-name] | vrf vrf-name]


      Example:
      Device(config)# address-family ipv4 vrf v1
       

      Enters address family configuration mode to configure a routing session using standard IP Version 4 (IPv4) address prefixes.

       
      Step 5no neighbor {ipv4-address | ipv6-address} translate-update multicast [unicast]


      Example:
      Device(config-af)# no neighbor 10.1.1.1 translate-update multicast unicast
       

      Disables multicast routing on devices, which are not capable of multicast BGP (mBGP) routing.

       
      Step 6 end


      Example:
      Device(config-af)# end
       

      Returns to privileged EXEC mode.

       
      Step 7show running-config


      Example:
      Device# show running-config
      
       

      Displays the running configuration on the device.

       

      Configuration Examples for VRF Aware BGP Translate-Update

      Example: Configuring VRF aware BGP Translate-Update

      The following example shows how to configure the translate-update feature for an IPv4 VRF address-family named v1 and BGP neighbor n2 peer-group for VRF configuration:


      Note


      Peer-template configuration for BGP neighbor is not supported for this feature due to conflicts with the earlier versions of Cisco software.
      Device> enable
      Device# configure terminal
      Device(config)# router bgp 65000
      Device(config-router)# address-family ipv4 vrf v1
      Device(config-router-af)# neighbor n2 peer-group
      Device(config-router-af)# neighbor n2 remote-as 4
      Device(config-router-af)# neighbor 10.1.1.1 peer-group n2
      Device(config-router-af)# neighbor 10.1.1.1 activate
      Device(config-router-af)# neighbor 10.1.1.1 translate-update multicast unicast
      Device(config-router-af)# end
      

      The following is sample output from the show bgp vpnv4 multicast vrf command. As the VRF aware BGP translate-update feature is configured, the state of the neighbor displays “NoNeg”:

      Device# show bgp vpnv4 multicast vrf v1 summary
      
      BGP router identifier 10.1.3.1, local AS number 65000
      BGP table version is 8, main routing table version 8
      7 network entries using 1792 bytes of memory
      8 path entries using 960 bytes of memory
      5/3 BGP path/bestpath attribute entries using 1280 bytes of memory
      3 BGP AS-PATH entries using 88 bytes of memory
      2 BGP extended community entries using 48 bytes of memory
      0 BGP route-map cache entries using 0 bytes of memory
      0 BGP filter-list cache entries using 0 bytes of memory
      BGP using 4168 total bytes of memory
      BGP activity 23/2 prefixes, 33/9 paths, scan interval 60 secs
       
      Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
      10.1.1.1        4            4       5      10        1    0    0 00:01:10 (NoNeg)                         
      10.1.3.2        4            2      12      10        8    0    0 00:01:33  
      

      The following is sample output from the show ip route multicast vrf command:


      Note


      The routes configured using the translate-update feature does not have the “+” symbol against the prefixes in the Routing Information Base (RIB) table. Appearance of the symbol in the first entry indicates that the unicast route has leaked into the multicast table. However, the second entry is a translate-update route, which appears to be a multicast route.
      Device# show ip route multicast vrf v1
      
      B   +    10.1.1.0/24 [20/0] via 10.1.1.1 (v1), 00:00:08
       
      B        10.1.1.0/24 [20/0] via 10.1.1.1 (v1), 00:00:42
       
      

      The following is sample output from the show running-config command:


      Note


      The provider-edge (PE) device must activate its BGP neighbor under the multicast address-family even though the neighbor is not capable of multicast routing. If the unicast address-family identifier has the route-map configured and multicast address-family identifier has no route-map configured, the unicast route-map controls the route under the unicast table but not the route under multicast table.
      Device# show running-config
      
      address-family ipv4 vrf v1
      redistribute connected
      redistribute static
      neighbor 10.1.1.1 remote-as 4
      neighbor 10.1.1.1 activate
      neighbor 10.1.1.1 translate-update multicast unicast
      neighbor 10.1.1.1 remote-as 4
      neighbor 10.1.1.1 activate
      exit-address-family
      !
      address-family ipv4 multicast vrf v1
      redistribute connected
      redistribute static
      neighbor 10.1.1.1 remote-as 4
      neighbor 10.1.1.1 activate
      neighbor 10.1.1.1 soft-reconfiguration inbound    
      neighbor 10.1.1.1 route-map x in 
      exit-address-family
        
      

      Note


      The “neighbor 10.1.1.1 soft-reconfiguration inbound” and the “ neighbor 10.1.1.1 route-map x in” field in the output indicate that only the routes in the BGP multicast table are affected.

      The following is sample output from the show running-config command when you configure a neighbor under different address-families:


      Note


      Configuring the BGP neighbor under different address-families manipulates the unicast routes and multicast routes advertised to the neighbor.

      Configuration for IPv4/IPv6 unicast address-family:

      Device# show running-config
      
      address-family ipv4
      neighbor 20.2.2.1 activate
      neighbor 20.2.2.1 translate-update multicast unicast  
      exit-address-family  
      !
      address-family ipv4 multicast
      neighbor 20.2.2.1 activate
      exit-address-family
      ! 
      

      Configuration for IPv4/IPv6 VRF unicast address-family:

      Device# show running-config
      
      address-family ipv4 vrf v1
      neighbor 20.2.2.1 remote-as 4
      neighbor 20.2.2.1 activate
      neighbor 20.2.2.1 translate-update multicast unicast 
      exit-address-family  
      !
      address-family ipv4 multicast vrf v1
      neighbor 20.2.2.1 remote-as 4
      neighbor 20.2.2.1 activate
      exit-address-family
      !  
      

      The following is sample configuration of the translate-update feature from a device with the old version of Cisco Software. The neighbor, in this case, is configured for IPv4/IPv6 unicast address-family, without running the address-family command:

      Configuration in the old format, without an address-family configured:

      Device> enable
      Device# configure terminal
      Device(config)# router bgp 65000
      Device(config-router)# neighbor 20.2.2.1 remote-as 4
      Device(config-router)# neighbor 20.2.2.1 translate-update nlri ipv4 multicast unicast 
      Device(config-router-af)# end  
      

      Configuration in the new format, without an address-family configured:

      Device> enable
      Device# configure terminal
      Device(config)# router bgp 65000
      Device(config-router)# neighbor 20.2.2.1 remote-as 4
      Device(config-router)# neighbor 20.2.2.1 translate-update nlri multicast unicast 
      Device(config-router-af)# end  
      

      Example: Removing VRF aware BGP Translate-Update Configuration

      The following example shows how to disable the VRF aware BGP translate-update feature for an IPv4 VRF address-family named v1 and BGP neighbor n2 peer-group for VRF:


      Note


      Disabling the translate-update configuration for a neighbor deletes the pseudo multicast neighbor and flaps the session, similar to removing the neighbor from a multicast session:
      Device> enable
      Device# configure terminal
      Device(config)# router bgp 65000
      Device(config-router)# address-family ipv4 vrf v1
      Device(config-router-af)# no neighbor 10.1.1.1 translate-update multicast unicast
      Device(config-router-af)# end
      

      The following output displays the debug logs after you disable the translate-update feature on the neighbor:

      *Nov 20 07:09:15.902: %BGP_SESSION-5-ADJCHANGE: 
      neighbor 2.2.2.1 IPv4 Multicast vpn vrf v1 topology base removed from session  Neighbor deleted
      *Nov 20 07:09:15.902: %BGP-5-ADJCHANGE: 
      neighbor 2.2.2.1 vpn vrf v1 Down Neighbor deleted
      *Nov 20 07:09:15.902: %BGP_SESSION-5-ADJCHANGE: 
      neighbor 2.2.2.1 IPv4 Unicast vpn vrf v1 topology base removed from session  Neighbor deleted
      *Nov 20 07:09:16.877: %BGP-5-ADJCHANGE: 
      neighbor 2.2.2.1 vpn vrf v1 Up 
      

      The following is sample output from the show running-config command:


      Note


      The associated neighbor 10.1.1.1 is removed even from the nonvolatile generation (NVGEN) after translate-update is disabled on that neighbor.
      Device# show running-config
      
      address-family ipv4 vrf v1
      redistribute connected
      redistribute static
      neighbor 10.1.1.1 remote-as 4
      neighbor 10.1.1.1 activate
      exit-address-family
      !
      address-family ipv4 multicast vrf v1
      redistribute connected
      redistribute static   
      exit-address-family 
      

      Additional References for VRF Aware BGP Translate-Update

      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 VRF Aware BGP Translate-Update

      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 VRF Aware BGP Translate-Update

      Feature Name

      Releases

      Feature Information

      VRF aware BGP Translate-Update

      15.4(2)T

      The VRF aware BGP translate-update feature enables multicast forwarding on those customer-edge (CE) devices, which have an older version of Cisco software that does not support multicast BGP (mBGP) routing.

      The following command was introduced:

      neighbor translate-update