Multitopology Routing Configuration Guide, Cisco IOS Release 15S
MTR Support for Multicast
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MTR Support for Multicast

MTR Support for Multicast

The MTR Support for Multicast feature provides Multitopology Routing (MTR) support for multicast and allows you to control the path of multicast traffic in the network. This module describes how to configure MTR support for multicast.

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.

Restrictions for MTR Support for Multicast

Only a single multicast topology can be configured, and only the topology base command can be entered when the multicast topology is created.

Information About MTR Support for Multicast

Overview of Multicast MTR in VRF

Cisco software supports legacy (pre-Multitopology Routing (MTR) IP multicast behavior by default. MTR support for IP multicast must be explicitly enabled. Legacy IP multicast uses reverse path forwarding (RPF) on routes in the unicast Routing Information Base (RIB) to build multicast distribution trees (MDTs).

MTR introduces a multicast topology that is completely independent from the unicast topology. MTR integration with multicast allows you to control the path of multicast traffic in the network.

The multicast topology maintains separate routing and forwarding tables. The following list summarizes MTR multicast support that is integrated into Cisco software:

  • Conventional longest match support for multicast routes.
  • RPF support for Protocol Independent Multicast (PIM).
  • Border Gateway Protocol (BGP) MDT subaddress family identifier (SAFI) support for Inter-AS VPNs (SAFI number 66).
  • Support for static multicast routes integrated into the ip route topology command (modifying the ip mroute command).

As in pre-MTR software, you enable multicast support by configuring the ip multicast-routing command in global configuration mode. You enable MTR support for multicast by configuring the ip multicast rpf multitopology command. After the device enters global address family configuration mode, you then enter the topology command with the base keyword; global topology configuration parameters are applied in this mode.

How to Configure MTR Support for Multicast

Configuring a Multicast Topology for MTR

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    ip multicast-routing [vrf name]

    4.    ip multicast rpf multitopology

    5.    global-address-family ipv4 [multicast | unicast]

    6.    topology {base | topology-name}

    7.    route-replicate from {multicast | unicast} [topology {base | name}] protocol [route-map name | vrf name]

    8.    use-topology unicast {base | topology-name}

    9.    shutdown

    10.    end

    11.    show topology [cache [topology-id] | ha [detail | interface | lock | router] [all | ipv4 | ipv6 | vrf vpn-instance]]


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 ip multicast-routing [vrf name]


    Example:
    Device(config)# ip multicast-routing 
     

    Enables IP multicast routing.

     
    Step 4 ip multicast rpf multitopology


    Example:
    Device(config)# ip multicast rpf multitopology 
     

    Enables Multitopology Routing (MTR) support for IP multicast routing.

     
    Step 5 global-address-family ipv4 [multicast | unicast]


    Example:
    Device(config)# global-address-family ipv4 multicast
     

    Enters global address family configuration mode to configure the global topology.

    • The address family for the class-specific topology is specified in this step. The subaddress family can be specified. Unicast is the default if no subaddress family is entered.
     
    Step 6 topology {base | topology-name}


    Example:
    Device(config-af)# topology base 
     

    Configures the global topology instance and enters address family topology configuration mode.

    • Only the base keyword can be accepted for a multicast topology.
     
    Step 7 route-replicate from {multicast | unicast} [topology {base | name}] protocol [route-map name | vrf name]


    Example:
    Device(config-af-topology)# route-replicate from unicast topology VOICE ospf route-map map1
     

    (Optional) Replicates (copies) routes from another multicast topology Routing Information Base (RIB).

    • The protocol argument is configured to specify the protocol that is the source of the route. Routes can be replicated from the unicast base topology or a class-specific topology.
    Note   

    However, route replication cannot be configured from a class-specific topology that is configured to forward the base topology (incremental forwarding). You can replicate routes from a multicast RIB to a multicast RIB or replicate routes from a unicast RIB to a multicast RIB, but you cannot replicate routes from a multicast RIB to a unicast RIB.

    • Replicated routes can be filtered through a route map before they are installed into the multicast RIB.
     
    Step 8 use-topology unicast {base | topology-name}


    Example:
    Device(config-af-topology)# use-topology unicast VIDEO 
     

    (Optional) Configures a multicast topology to perform reverse path forwarding (RPF) computations using a unicast topology RIB.

    • The base or a class-specific unicast topology can be configured. When this command is configured, the multicast topology uses routes in the specified unicast topology table to build multicast distribution trees.
    Note   

    This multicast RIB is not used when this command is enabled, even if the multicast RIB is populated and supported by a routing protocol.

     
    Step 9 shutdown


    Example:
    Device(config-af-topology)# shutdown 
     

    (Optional) Temporarily disables a topology instance without removing the topology configuration (while other topology parameters are configured and other devices are configured with MTR).

     
    Step 10 end


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

    (Optional) Exits address family topology configuration mode and enters privileged EXEC mode.

     
    Step 11 show topology [cache [topology-id] | ha [detail | interface | lock | router] [all | ipv4 | ipv6 | vrf vpn-instance]]


    Example:
    Device# show topology detail
     

    (Optional) Displays information about class-specific and base topologies.

     

    What to Do Next

    The topology is not activated until classification is configured. See the “QoS-MQC Support for MTR” feature module to configure classification for a class-specific topology.

    Configuration Examples for MTR Support for Multicast

    Examples: Route Replication Configuration

    The following example shows how to enable multicast support for Multitopology Routing (MTR) and to configure a separate multicast topology:

    ip multicast-routing
    ip multicast rpf multitopology
    !
    global-address-family ipv4 multicast
     topology base
     end 
    

    The following example shows how to configure the multicast topology to replicate Open Shortest Path First (OSPF) routes from the VOICE topology. The routes are filtered through the VOICE route map before they are installed in the multicast routing table.

    ip multicast-routing
    ip multicast rpf multitopology
    !
    access-list 1 permit 192.168.1.0 0.0.0.255
    !
    route-map VOICE
     match ip address 1
     exit 
    !
    global-address-family ipv4 multicast
     topology base
     route-replicate from unicast topology VOICE ospf route-map VOICE 

    Example: Using a Unicast RIB for Multicast RPF Configuration

    The following example shows how to configure the multicast topology to perform reverse path forwarding (RPF) calculations on routes in the VIDEO topology Routing Information Base (RIB) to build multicast distribution trees:

    ip multicast-routing
    ip multicast rpf multitopology
    !
    global-address-family ipv4 multicast
     topology base
     use-topology unicast VIDEO
     end 

    Example: Multicast Verification

    The following example shows that the multicast topology is configured to replicate routes from the Routing Information Base (RIB) of the VOICE topology:

    Device# show topology detail 
    
    Topology: base
      Address-family: ipv4
      Associated VPN VRF is default
      Topology state is UP
      Associated interfaces:
        Ethernet0/0, operation state: UP
        Ethernet0/1, operation state: DOWN
        Ethernet0/2, operation state: DOWN
        Ethernet0/3, operation state: DOWN
        Loopback0, operation state: UP
              
    Topology: VIDEO
      Address-family: ipv4
      Associated VPN VRF is default
      Topology state is UP
      Topology fallback is enabled
      Topology maximum route limit 1000, warning limit 90% (900)
      Associated interfaces:
    Topology: VOICE
      Address-family: ipv4
      Associated VPN VRF is default
      Topology state is UP
      Topology is enabled on all interfaces
      Associated interfaces:
        Ethernet0/0, operation state: UP
        Ethernet0/1, operation state: DOWN
        Ethernet0/2, operation state: DOWN
        Ethernet0/3, operation state: DOWN
        Loopback0, operation state: UP
    Topology: base
      Address-family: ipv4 multicast
      Associated VPN VRF is default
      Topology state is DOWN
      Multicast multi-topology mode is enabled.
      Route Replication Enabled:
        from unicast topology VOICE all route-map VOICE
      Associated interfaces:

    Additional References

    Related Documents

    Related Topic

    Document Title

    Cisco IOS commands

    Cisco IOS Master Command List, All Releases

    Multitopology Routing (MTR) commands

    Cisco IOS Multitopology Routing Command Reference

    IP multicast commands

    Cisco IOS Multicast Command Reference

    IP multicast concepts and tasks

    IP Multicast Configuration Guide Library

    Technical Assistance

    Description

    Link

    The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

    http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

    Feature Information for MTR Support for Multicast

    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 MTR Support for Multicast

    Feature Name

    Releases

    Feature Information

    MTR Support for Multicast

    12.2(33)SRB

    15.0(1)M

    15.0(1)SY

    15.1(1)SY

    This feature provides Multitopology Routing (MTR) support for multicast and allows you to control the path of multicast traffic in the network.

    The following commands were introduced or modified: clear ip route multicast, ip multicast rpf multitopology, show ip route multicast, use-topology.