HP A8800 Configuration Manual page 76

As shown in Figure 24, when no static multicast route is configured, Router C's RPF neighbor on the path
back to the source is Router A and the multicast information from the source travels along the path from
Router A to Router C, which is the unicast route between the two routers; with a static route configured on
Router C and Router B as Router C's RPF neighbor on the path back to the source, the multicast
information from the source travels from Router A to Router B and then to Router C.
Creating an RPF route
When a unicast route is blocked, multicast traffic forwarding is stopped due to 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.
Figure 25 Creating an RPF route
As shown in Figure 25, the RIP domain and the OSPF domain are unicast isolated from each other.
When no static multicast route is configured, the hosts (the receivers) in the OSPF domain cannot receive
the multicast packets sent by the multicast source (the source) in the RIP domain. After you configure a
static multicast route on Router C and Router D, specifying Router B as the RPF neighbor of Router C and
specifying Router C as the RPF neighbor of Router D, the receivers can receive multicast data sent by the
multicast source.
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