Users Guide

• trac concentration: PIM-SM allows only one active group to RP mapping which means that all trac 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 eective as trac increases because preemptive load balancing requires prior
knowledge of trac 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 congure 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 signicant manner
according to the locations of the sources and receivers.
1 All the RPs serving a given group are congured with an identical anycast address.
2 Sources then register with the topologically closest RP.
3 RPs use MSDP to peer with each other using a unique address.
Figure 79. MSDP with Anycast RP
Conguring Anycast RP
To congure anycast RP, use the following commands.
1 In each routing domain that has multiple RPs serving a group, create a Loopback interface on each RP serving the group with the
same IP address.
Multicast Source Discovery Protocol (MSDP)
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