[Contents] [Prev] [Next] [Index] [Report an Error]

Anycast RP

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.

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.

When anycast RP is configured, the shared address is used in the RP-to-group mapping. This allows multicast groups to have multiple active RPs in a PIM domain. However, the RPs must use some protocol to synchronize the active source information so that the active RP for each group is known to all RPs.

There are two methods for RP active source synchronization in anycast RP, one using the Multicast Source Discovery Protocol (MSDP) and the other using PIM itself.

When MSDP is used with PIM sparse mode, anycast RP provides a faster failover rate than auto-RP or a bootstrap router. However, MSDP only works for IPv4. When PIM alone is used for anycast RP, the solution works for both IPv4 and IPv6.

For more information about configuring static RPs, see Configuring Static RPs. For more information about configuring anycast RP, see Configuring Auto-RP and Example: Configuring Anycast RP.

[Contents] [Prev] [Next] [Index] [Report an Error]