Multitopology Routing Configuration Guide, Cisco IOS Release 15SY
MTR Support for Multicast
MTR Support for Multicast
Last Updated: October 15, 2012
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.
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Restrictions for MTR Support for Multicast
Information About MTR Support for Multicast
MTR Support for Multicast
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:
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
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:
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.
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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.
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