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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 given multicast source to change the RPF route to create a transmission path for
multicast traffic that is different from that for unicast traffic.
Figure 27 Changing an RPF route
As shown in Figure 27, when no static multicast route is configured, Switch C's RPF neighbor on the path
back to Source is Switch A. The multicast information from Source travels along the path from Switch A
to Switch C, which is the unicast route between the two routers. When a static multicast route is
configured on Switch C and Switch B is configured as Switch C's RPF neighbor on the path back to
Source, the multicast information from Source travels from Switch A to Switch B and then to Switch C.
Creating an RPF route
When a unicast route is blocked, multicast traffic forwarding might be stopped because of lack of an RPF
route. By configuring a static multicast route for a given multicast source, you can create an RPF route so
that a multicast routing entry is created to guide multicast traffic forwarding regardless of whether a
unicast route is available.
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