For more information about the concepts of designated router (DR), bootstrap router (BSR),
candidate-BSR (C-BSR), rendezvous point (RP), candidate RP (C-RP), shortest path tree (SPT) and

rendezvous point tree (RPT) mentioned in this document, see PIM Configuration in the IP
Multicast Volume

MSDP Overview

Introduction to MSDP

Multicast source discovery protocol (MSDP) is an inter-domain multicast solution developed to address

the interconnection of protocol independent multicast sparse mode (PIM-SM) domains. It is used to
discover 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 of a domain is isolated from that of another domain. As a result, the RP

is aware of 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. If

there is a mechanism that allows RPs of different PIM-SM domains to share their multicast source
information, the local RP will be able to join multicast sources in other domains and multicast data can

be transmitted among different domains.
MSDP achieves this goal. With MSDP peer relationships established between appropriate routers in the

network, the RPs of different PIM-SM domains are interconnected with one another. Source active (SA)

messages are exchanged between these MSDP peers and thus the multicast source information is shared

among these different domains.

CAUTION:
•

MSDP is applicable only if the intra-domain multicast protocol is PIM-SM.

•

MSDP is meaningful only for the any-source multicast (ASM) model.

This manual is related to the following products:

H3C SecPath F5000-A5 Firewall H3C SecBlade FW Cards H3C SecPath U200-A U200-M U200-S