4000 Router Series IP Multicast Configuration Guide

Figure 15 Changing an RPF route

As shown in Figure 15, 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 data from the source travels through Router A to Router

C. When a static multicast route is configured on Router C with Router B as its RPF neighbor on the path

back to the source, the multicast data from the source travels along the path: Router A to Router B and

then to Router 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 given multicast source,

so that a multicast routing entry is created to guide multicast forwarding.

Figure 16 Creating an RPF route

As shown in Figure 16, the RIP domain and the OSPF domain are unicast isolated from each other. When

no static multicast route is configured, the receiver hosts in the OSPF domain cannot receive the multicast

packets from the multicast source in the RIP domain. If you configure a static multicast route on Router C

Eth1/1

1.1.1.2/24

Eth1/2

1.1.1.1/24

Eth1/2

2.2.2.2/24

Eth1/1

2.2.2.1/24

Source

192.168.0.1/24

Source/Mask

Multicast Routing Table Static on Router C

192.168.0.0/24

Interface

Eth1/1

RPF neighbor/Mask

1.1.1.1/24

Source/Mask

Multicast Routing Table Static on Router D

192.168.0.0/24

Interface

Eth1/1

RPF neighbor/Mask

2.2.2.2/24

OSPF domain

RIP domain

Router A Router B Router C

Router D

Receiver

Multicast packets Multicast static route