Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 82)

70 Multi-Service IronWare Multicast Configuration Guide
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Configuring Multicast Source Discovery Protocol (MSDP)
1
In this example, the source for PIM Sparse multicast group 232.0.1.95 is in PIM Sparse domain 1.
The source sends a packet for the group to its directly attached DR. The DR sends a Group
Advertisement message for the group to the RP for the domain. The RP is configured for MSDP,
which enables the RP to exchange source information with other PIM Sparse domains by
communicating with RPs in other domains that are running MSDP.
The RP sends the source information to each peer through a Source Active message. The message
contains the IP address of the source, the group address to which the source is sending, and the IP
address of the RP.
In this example, the Source Active message contains the following information:
• Source address: 206.251.14.22
• Group address: 232.1.0.95
• RP address: 206.251.17.41
Figure 9 shows only one peer for the MSDP device (which is also the RP here) in domain 1, so the
Source Active message goes to only that peer. When an MSDP device has multiple peers, it sends a
Source Active message to each of those peers. Each peer sends the Source Advertisement to other
MSDP peers. The RP that receives the Source Active message also sends a Join message to the
source if the RP that received the message has receivers for the group and source.
Peer Reverse Path Forwarding (RPF) flooding
When the MSDP device (also the RP) in domain 2 receives the Source Active message from the
peer in domain 1, the MSDP device in domain 2 forwards the message to all other peers. This
propagation process is sometimes called “peer Reverse Path Forwarding (RPF) flooding”. In
Figure 9 , the MSDP device floods the Source Active message it receives from the peer in domain 1
to peers in domains 3 and 4.