PIM Anycast RP (rendezvous point) provides load balancing and fast convergence to PIM RPs in an IPv4 multicast domain. The RP address of the Anycast RP is a shared address used among multiple PIM routers, known as PIM RP. The PIM RP routers create an Anycast RP set. Each router in the Anycast RP set is configured using two IP addresses: a shared RP address in their loopback address and a separate, unique IP address. The loopback address must be reachable by all PIM routers in the multicast domain. The separate, unique IP address is configured to establish static peering with other PIM routers and communication with the peers.
When the source is activated in a PIM Anycast RP domain, the PIM First Hop (FH) registers the source to the closest PIM RP. The PIM RP follows the same MSDP (Multicast Source Discovery Protocol) Anycast RP operation by decapsulating the packet and creating the (s,g) state. When there are external peers in the Anycast RP set, the router re-encapsulates the packet with the local peering address as the source address of the encapsulation. The router unicasts the packet to all Anycast RP peers. The re-encapsulation of the data register packet to Anycast RP peers ensures source state distribution to all RPs in a multicast domain.
The following example is a PIM Anycast-enabled network with 3 RPs and 1 PIM-FH router connecting to its active source and local receiver. Loopback 1 in RP1, RP2, and RP3 have the same IP address: 100.1.1.1. Each Loopback 2 in RP1, RP2, and RP3 has a separate IP address configured to communicate with their peers in the Anycast RP set.
