Static multicast routes

Depending on the application environment, a static multicast route can change an RPF route or create an RPF route.

Changing an RPF route

Typically, the topology structure of a multicast network is the same as that of a unicast network, and multicast traffic follows the same transmission path as unicast traffic does. You can configure a static multicast route for a multicast source to change the RPF route. As a result, the router creates a transmission path for multicast traffic that is different from the transmission path for unicast traffic.

Figure 23: Changing an RPF route

As shown in Figure 23, when no static multicast route is configured, Switch C's RPF neighbor on the path back to the source is Switch A. The multicast data from the source travels through Switch A to Switch C. You can configure a static multicast route on Switch C and specify its RPF neighbor on the route back to the source as Switch B. Then, the multicast data from the source travels along the path: Switch A to Switch B and then to Switch C.

Creating an RPF route

When a unicast route is blocked, multicast forwarding might be stopped due to lack of an RPF route. In this case, you can create an RPF route by configuring a static multicast route for a multicast source. Then, a multicast routing entry is created to guide multicast forwarding.

Figure 24: Creating an RPF route

As shown in Figure 24, the RIP domain and the OSPF domain are unicast isolated from each other. For the receiver hosts in the OSPF domain to receive multicast packets from the multicast source in the RIP domain, you must configure Switch C and Switch D as follows:


[NOTE: ]

NOTE:

A static multicast route is effective only on the multicast router on which it is configured, and will not be advertised throughout the network or redistributed to other routers.