83Figure 28 Creating an RPF routeAs shown in Figure 28, the RIP domain and the OSPF domain are unicast isolated from each other. Whenno static multicast route is configured, the hosts (the receivers) in the OSPF domain cannot receive themulticast packets that the multicast source (the source) sent in the RIP domain. After you configure a staticmulticast route on Switch C and Switch D, specifying Switch B as the RPF neighbor of Switch C andspecifying Switch C as the RPF neighbor of Switch D, the receivers can receive multicast data that themulticast 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 configured, and will not beadvertised throughout the network or redistributed to other routers.Multicast forwarding across unicast subnetsSome networking devices might not support multicast protocols in a network. Multicast devices forwardmulticast traffic from a multicast source hop by hop along the forwarding tree. When the multicast trafficis forwarded to a next-hop device that does not support IP multicast, the forwarding path is blocked. Inthis 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-int101.1.1.2/24Vlan-int101.1.1.1/24Vlan-int202.2.2.2/24Vlan-int202.2.2.1/24Source192.168.0.1/24Source/MaskMulticast Routing Table Static on Switch C192.168.0.0/24InterfaceVlan-int10RPF neighbor/Mask1.1.1.1/24Source/MaskMulticast Routing Table Static on Switch D192.168.0.0/24InterfaceVlan-int20RPF neighbor/Mask2.2.2.2/24OSPF domainRIP domainSwitch A Switch B Switch CSwitch D ReceiverReceiverMulticast packets Multicast static route
