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Configuring MSDP
This chapter describes MSDP, how to configure MSDP, configuration examples, and troubleshooting
methods.
Overview
MSDP is an inter-domain multicast solution that addresses the interconnection of PIM-SM domains.
It discovers multicast source information in other PIM-SM domains.
In the basic PIM-SM mode, a multicast source registers only with the RP in the local PIM-SM domain,
and the multicast source information about a domain is isolated from that of another domain. As a
result, the RP obtains the source information only within the local domain, and a multicast distribution
tree is built only within the local domain to deliver multicast data from a local multicast source to local
receivers. MSDP enables the RPs of different PIM-SM domains to share their multicast source
information, so that the local RP can join multicast sources in other domains, and multicast data can
be transmitted among different domains.
With MSDP peer relationship established between appropriate routers in the network, the RPs of
different PIM-SM domains are interconnected with one another. These MSDP peers exchange
source active (SA) messages, so that the multicast source information is shared among these
different domains.
For more information about the concepts of DR, BSR, C-BSR, RP, C-RP, SPT, and RPT mentioned in
this document, see "
The term "interface" in this chapter collectively refers to
Layer 3 interfaces, including
VLAN interfaces
and Layer 3 Ethernet interfaces. You can set an Ethernet port as a Layer 3 interface by using the
port link-mode route
command (see
Layer 2—LAN Switching Configuration Guide
).
NOTE:
MSDP is applicable only if the intra-domain multicast protocol is PIM-SM and is meaningful only for
the ASM model.
How MSDP operates
MSDP peers
One or more pairs of MSDP peers in the network forms an MSDP interconnection map, where the
RPs of different PIM-SM domains are interconnected in a series. An SA message that an RP sends
and these MSDP peers relay can be delivered to all other RPs.
