RP Mapping with Anycast RP

Having a single active RP per multicast group is much the same as having a single server providing any service. All traffic converges on this single point, although other servers are sitting idle, and convergence is slow when the resource fails. In multicast specifically, there might be closer RPs on the shared tree, so the use of a single RP is suboptimal.

For the purposes of load balancing and redundancy, you can configure anycast RP. You can use anycast RP within a domain to provide redundancy and RP load sharing. When an RP goes down, sources and receivers are taken to a new RP by means of unicast routing. When you configure anycast RP, you bypass the restriction of having one active RP per multicast group, and instead deploy multiple RPs for the same group range. The RP routers share one unicast IP address. Sources from one RP are known to other RPs that use MSDP. Sources and receivers use the closest RP, as determined by the interior gateway protocol (IGP).

Anycast means that multiple RP routers share the same unicast IP address. Anycast addresses are advertised by the routing protocols. Packets sent to the anycast address are sent to the nearest RP with this address. Anycast addressing is a generic concept and is used in PIM sparse mode to add load balancing and service reliability to RPs.

Anycast RP is defined in Internet draft draft-ietf-mboned-anycast-rp-08.txt, Anycast RP Mechanism Using PIM and MSDP. To access Internet RFCs and drafts, go to the IETF Web site at http://www.ietf.org.

Related Topics

• Configuring the Static PIM RP Address on the Non-RP Routing Device
• Example: Configuring Multiple RPs in a Domain with Anycast RP
• Example: Configuring PIM Anycast with or without MSDP
• Example: Configuring PIM Anycast with or without MSDP