Figure 86. MSDP SA Message FormatAnycast RPUsing MSDP, anycast RP provides load sharing and redundancy in PIM-SM networks. Anycast RP allows two or more rendezvouspoints (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 Loopbackaddress are configured with a 32-bit mask, making it a host address. All downstream routers are configured to know that the AnycastRP Loopback address is the IP address of their local RP. IP routing automatically selects the closest RP for each source and receiver.Assuming that the sources are evenly spaced around the network, an equal number of sources register with each RP. Consequently,all the RPs in the network share the process of registering the sources equally. Because a source may register with one RP andreceivers may join to a different RP, a method is needed for the RPs to exchange information about active sources. This informationexchange is done with MSDP.With Anycast RP, all the RPs are configured to be MSDP peers of each other. When a source registers with one RP, an SA messageis sent to the other RPs informing them that there is an active source for a particular multicast group. The result is that each RP isaware of the active sources in the area of the other RPs. If any of the RPs fail, IP routing converges and one of the RPs becomesthe active RP in more than one area. New sources register with the backup RP. Receivers join toward the new RP and connectivityis maintained.Implementation InformationThe Dell Networking OS implementation of MSDP is in accordance with RFC 3618 and Anycast RP is in accordance with RFC 3446.Configure Multicast Source Discovery ProtocolConfiguring MSDP is a four-step process.1. Enable an exterior gateway protocol (EGP) with at least two routing domains.Refer to the following figures.The MSDP Sample Configurations show the OSPF-BGP configuration used in this chapter for MSDP. Also, refer to OpenShortest Path First (OSPFv2) and Border Gateway Protocol IPv4 (BGPv4).2. Configure PIM-SM within each EGP routing domain.Refer to the following figures.The MSDP Sample Configurations show the PIM-SM configuration in this chapter for MSDP. Also, refer to PIM Sparse-Mode(PIM-SM).520 Multicast Source Discovery Protocol (MSDP)
