Configuring an RP Router for PIM Sparse Mode and PIM Sparse-Dense Mode

When you use the router for PIM sparse mode or PIM sparse-dense mode, some VRs must act as RP routers. You can configure static RP routers or configure the router to assign RP routers automatically.

To configure the router to assign RP routers automatically, you must define several VRs as RP routers and one VR as an RP mapping agent. RP routers send their announcement messages to the RP mapping agent, which assigns groups to RP routers and resolves any conflicts. The RP mapping agent notifies neighbors of the RP assigned to each group.

Configuring a Static RP Router

If you want to control PIM more tightly, you can configure a static RP router. To do so:

1. Configure an access list that specifies the multicast groups that can use the static RP router.
   host1(config)#access-list boston permit 228.0.0.0 15.255.255.255
2. Specify a static RP router.
   host1(config)#ip pim rp-address 122.0.0.1 1 boston

Configuring an Auto-RP Router for PIM Sparse Mode

Two multicast groups, 224.0.1.39 and 224.0.1.40, are reserved for forwarding auto-RP messages through the network. When you configure an auto-RP router for PIM sparse mode, you must assign a static RP router to these two groups. You can then specify an RP mapping agent for other multicast groups.

To configure an auto-RP router for PIM sparse mode:

1. Configure a static RP to have priority over the auto-RP for the groups that send auto-RP multicast messages.
   host1(config)#access-list 11 permit 224.0.1.39 0.0.0.0 host1(config)#access-list 11 permit 224.0.1.40 0.0.0.0 host1(config)#ip pim rp-address 192.48.1.22 11 override
2. Assign an RP mapping agent.
   host1(config)#ip pim send-rp-discovery scope 23 loopback 1
3. Configure routers to send auto-RP announcement messages to the mapping agent.
   host1(config)#ip pim send-rp-announce loopback 2 scope 16 group-list 1

Configuring an Auto-RP Router for PIM Sparse-Dense Mode

In PIM sparse-dense mode, you must prevent routers from advertising auto-RP messages to the multicast groups 224.0.1.39 and 224.0.1.40, which are reserved for forwarding auto-RP messages through the network. To configure an auto-RP router for PIM sparse-dense mode:

1. Assign an RP mapping agent.
   host1(config)#ip pim send-rp-discovery scope 23 loopback 1
2. Configure an access list that details the multicast groups that can use the static RP router.
   host1(config)access-list boston permit 224.0.0.0 15.255.255.255
3. Prevent routers from advertising auto-RP messages to the multicast groups that are reserved for forwarding auto-RP messages through the network.
   host1(config)#access-list 1 deny 224.0.1.39 host1(config)#access-list 1 deny 224.0.1.40
4. Configure routers to send auto-RP announcement messages to the mapping agent.
   host1(config)#ip pim send-rp-announce loopback 2 scope 23 group-list boston interval 200