4000 Router Series IP Multicast Configuration Guide

and Router D, specifying Router B as the RPF neighbor of Router C and Router C as the RPF neighbor of

Router D, the receiver hosts can receive the multicast data from the multicast source.

NOTE:

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

Routers forward the multicast data from a multicast source hop by hop along the forwarding tree, but

some routers might not support multicast protocols in a network. When the multicast data is forwarded

to a router that does not support IP multicast, the forwarding path is blocked. In this case, you can enable

multicast forwarding across two unicast subnets by establishing a tunnel between the routers at the edges

of the two unicast subnets.

Figure 17 Multicast data transmission through a tunnel

As shown in Figure 17, with a tunnel established between the multicast routers Router A and Router B,

Router A encapsulates the multicast data in unicast IP packets, and forwards them to Router B across the

tunnel through unicast routers. Then, Router B strips off the unicast IP header and continues to forward the

multicast data to the receiver.

To use this tunnel only for multicast traffic, configure the tunnel as the outgoing interface only for multicast

routes.

Configuration task list

Tasks at a

lance

(Required.) Enabling IP multicast routing

(Optional.) Configuring multicast routing and forwarding

• (Optional.) Configuring static multicast routes

• (Optional.) Configuring the RPF route selection rule

• (Optional.) Configuring multicast load splitting

• (Optional.) Configuring a multicast forwarding boundary

• (Optional.) Configuring static multicast MAC address entries