RPs advertise each (S,G) in its domain in type, length, value (TLV) format. The total number of TLVs contained in the SA is indicated in the“Entry Count” field. SA messages are transmitted every 60 seconds, and immediately when a new source is detected.Figure 84. MSDP SA Message FormatTopics:• Anycast RP• Implementation Information• Configure Multicast Source Discovery Protocol• Enable MSDP• Manage the Source-Active Cache• Accept Source-Active Messages that Fail the RFP Check• Specifying Source-Active Messages• Limiting the Source-Active Messages from a Peer• Preventing MSDP from Caching a Local Source• Preventing MSDP from Caching a Remote Source• Preventing MSDP from Advertising a Local Source• Logging Changes in Peership States• Terminating a Peership• Clearing Peer Statistics• Debugging MSDP• MSDP with Anycast RP• Configuring Anycast RP• MSDP Sample ConfigurationsAnycast RPUsing MSDP, anycast RP provides load sharing and redundancy in PIM-SM networks. Anycast RP allows two or more rendezvous points(RPs) to share the load for source registration and the ability to act as hot backup routers for each other.Anycast RP allows you to configure two or more RPs with the same IP address on Loopback interfaces. The Anycast RP Loopback addressare configured with a 32-bit mask, making it a host address. All downstream routers are configured to know that the Anycast RP Loopbackaddress is the IP address of their local RP. IP routing automatically selects the closest RP for each source and receiver. Assuming that thesources are evenly spaced around the network, an equal number of sources register with each RP. Consequently, all the RPs in the networkshare the process of registering the sources equally. Because a source may register with one RP and receivers may join to a different RP, amethod is needed for the RPs to exchange information about active sources. This information exchange is done with MSDP.Multicast Source Discovery Protocol (MSDP) 535
