Inter-AS Multicast Using MBGP and MSDP
Both Multiprotocol Border Gateway Protocol (MBGP) and MSDP connections are TCP connections. Two MSDP peers can set up an MBGP peer relationship to ensure that SA messages can pass RPF checks.
As shown in Figure 1, the RPs in different PIM-SM domains are not directly connected to each other, and the RPs and ASBRs are deployed on different routers. After the RPs set up an MSDP peer relationship, they can also set up an MBGP peer relationship to ensure that SA messages can pass RPF checks.
IBGP: sets up IBGP peer relationships between RPs in the same AS, such as RP1 and RP2, and RP3 and RP4.
EBGP: sets up EBGP peer relationships between RPs in different ASs, such as RP1 and RP3, and RP2 and RP4.
The MBGP and MSDP peer relationship must be set up on the same interface. MBGP and MSDP are often used together. For details about MBGP, see BGP Configuration in the S2720, S5700, and S6700 V200R019C10 Configuration Guide - IP Unicast Routing.