83
Figure 28 Creating an RPF route
As shown in Figure 28, 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 that the multicast source (the source) sent in the RIP domain. After you configure a static
multicast route on Switch C and Switch D, specifying Switch B as the RPF neighbor of Switch C and
specifying Switch C as the RPF neighbor of Switch D, the receivers can receive multicast data that the
multicast source sent.
NOTE:
• Static multicast routes only affect RPF check but cannot guide multicast forwarding.
• A static multicast route is effective only on the multicast router on which it is confi
ured, and will not be
advertised throughout the network or redistributed to other routers.
Multicast forwarding across unicast subnets
Some networking devices might not support multicast protocols in a network. Multicast devices forward
multicast traffic from a multicast source hop by hop along the forwarding tree. When the multicast traffic
is forwarded to a next-hop device that does not support IP multicast, the forwarding path is blocked. In
this case, you can enable multicast traffic forwarding across the unicast subnet by establishing a tunnel,
such as an IPv4 over IPv4 tunnel, between the devices at both ends of the unicast subnet.
For more information about tunneling, see Layer 3—IP Services Configuration Guide.
Vlan-int10
1.1.1.2/24
Vlan-int10
1.1.1.1/24
Vlan-int20
2.2.2.2/24
Vlan-int20
2.2.2.1/24
Source
192.168.0.1/24
Source/Mask
Multicast Routing Table Static on Switch C
192.168.0.0/24
Interface
Vlan-int10
RPF neighbor/Mask
1.1.1.1/24
Source/Mask
Multicast Routing Table Static on Switch D
192.168.0.0/24
Interface
Vlan-int20
RPF neighbor/Mask
2.2.2.2/24
OSPF domain
RIP domain
Switch A Switch B Switch C
Switch D
Receiver
Receiver
Multicast packets Multicast static route
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