Users Guide

MSDP with Anycast RP
Anycast RP uses MSDP with PIM-SM to allow more than one active group to use RP mapping.
PIM-SM allows only active groups to use RP mapping, which has several implications:
• traffic concentration: PIM-SM allows only one active group to RP mapping which means that all traffic for the group must,
at least initially, travel over the same part of the network. You can load balance source registration between multiple RPs by
strategically mapping groups to RPs, but this technique is less effective as traffic increases because preemptive load
balancing requires prior knowledge of traffic distributions.
• lack of scalable register decasulation: With only a single RP per group, all joins are sent to that RP regardless of the
topological distance between the RP, sources, and receivers, and data is transmitted to the RP until the SPT switch
threshold is reached.
• slow convergence when an active RP fails: When you configure multiple RPs, there can be considerable convergence
delay involved in switching to the backup RP.
Anycast RP relieves these limitations by allowing multiple RPs per group, which can be distributed in a topologically significant
manner according to the locations of the sources and receivers.
1. All the RPs serving a given group are configured with an identical anycast address.
2. Sources then register with the topologically closest RP.
Multicast Source Discovery Protocol (MSDP) 483