Cisco Systems 78-11741-02 manual Configuring Both Routers to RPF, IPC-444

Configuring IP Multicast Routing

Load Splitting IP Multicast Traffic Across Equal-Cost Paths Configuration Task List

Configuring Both Routers to RPF

Because the use of the tunnel makes the multicast topology incongruent with the unicast topology, and only multicast traffic traverses the tunnel, you must configure the routers to reverse path forward correctly over the tunnel. The following sections describe two ways to configure the routers to reverse path forward multicast traffic over the tunnel, depending on your topology:

•Load Splitting to a Stub Network

•Load Splitting to the Middle of a Network

Load Splitting to a Stub Network

To load split to a stub network using a static multicast router, use the following command on the stub router in global configuration mode:

Command	Purpose
Router(config)# ip mroute 0.0.0.0 0.0.0.0	Configures a static multicast route over which to reverse path
tunnel number	forward from the stub router to the other end of the tunnel.

After configuring a static multicast route, use the following commands on the router at the opposite end of the tunnel from the stub router in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# ip mroute	Configures a static route over which to reverse path forward from
	source-address mask tunnel number	the access router to the other end of the tunnel. Configure the
		source-addressargument to be the network address of the network
		connected to the stub router.
Step 2
	Router(config)# ip mroute	Repeat Step 1 for each network connected to the stub router.
	source-address mask tunnel number

Load Splitting to the Middle of a Network

You can also use static mroutes to load split to the middle of a network, but you must make sure that Router A would reverse path forward to the tunnel for source networks behind Router B, and Router B would reverse path forward to the tunnel for source networks behind Router A.

Another option is to run a separate unicast routing protocol with a better administrative distance to provide the RPF. You must make sure that your multicast routers do not advertise the tunnel to your real network. For details, refer to the “Configuring an IP Multicast Static Route” section in this chapter.

If you are using a DVMRP routing table for RPF information within your network, you could configure the ip dvmrp unicast-routinginterface configuration command on your tunnel interfaces to make the routers reverse path forward correctly over the tunnel.

Cisco IOS IP Configuration Guide

IPC-444