MSDP Configuration Task List 1137from Source encapsulated in the SA message. When the SA message reaches RP 2,RP 2 decapsulates the message.4 Receivers receive the multicast data along the RPT and directly joins the SPT rootedat the multicast source. In this example, RP 2 forwards the multicast data downthe RPT. When Receiver receives the multicast data from Source, it directly joinsthe SPT rooted at Source.The significance of Anycast RP is as follows:■ Optimal RP path: A multicast source registers with the nearest RP so that anSPT with the optimal path is built; a receiver joins the nearest RP so that an RPTwith the optimal path is built.■ Load balancing between RPs: Each RP just needs to maintain part of thesource/group information within the PIM-SM domain and forward part of themulticast data, thus achieving load balancing between different RPs.■ Redundancy backup between RPs: When an RP fails, the multicast sourcepreviously registered on it or the receivers previous joined it will register with orjoin another nearest RP, thus achieving redundancy backup between RPs.c CAUTION:■ Be sure to configure a 32-bit subnet mask (255.255.255.255) for the AnycastRP address, namely configure the Anycast RP address into a host address.■ An MSDP peer address must be different from the Anycast RP address.Multi-Instance MSDP MSDP peering relationship can be built between multicast-enabled interfaces thatbelong to the same instance. Through exchanges of SA messages between MSDPpeers, the MSDP mechanism makes VPN multicast transmission between differentPIM-SM domains possible.A multicast router running multiple MSDP instances maintains an independent setof MSDP mechanism for each instance it supports, including SA cache, peeringconnection, timers, sending cache, and cache for exchanging information withPIM, while one instance is isolated from another; therefore, interoperabititybetween MSDP and PIM-SM is available only within the same instance.Protocols and Standards MSDP is documented in the following specifications:■ RFC 3618: Multicast Source Discovery Protocol (MSDP)■ RFC 3446: Anycast Rendezvous Point (RP) mechanism using ProtocolIndependent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP)MSDP ConfigurationTask ListComplete these tasks to configure MSDP:Task Remarks“Configuring Basic Functions ofMSDP” on page 1138“Enabling MSDP” on page1138Required“Creating an MSDP PeerConnection” on page 1139Required“Configuring a Static RPFPeer” on page 1139Optional
