Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 535

• 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. 3 RPs use MSDP to peer with each other using a unique address. Figure 89. MSDP with Anycast RP Configuring Anycast RP To configure 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) 535