Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 83)

Multi-Service IronWare Multicast Configuration Guide 71
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Configuring Multicast Source Discovery Protocol (MSDP)
1
The MSDP device in domain 2 does not forward the Source Active back to the peer in domain 1,
because that is the peer from which the device received the message. An MSDP device never
sends a Source Active message back to the peer that sent it. The peer that sent the message is
sometimes called the “RPF peer”. The MSDP device uses the unicast routing table for its Exterior
Gateway Protocol (EGP) to identify the RPF peer by looking for the route entry that is the next hop
toward the source. Often, the EGP protocol is Border Gateway Protocol (BGP) version 4.
NOTE
MSDP depends on BGP and MBGP for inter-domain operations.
The MSDP routers in domains 3 and 4 also forward the Source Active message to all peers except
the ones that sent them the message.
Figure 9 does not show additional peers.
Source Active caching
When an MSDP device that is also an RP and source receives a Source Active message, the RP and
source checks the PIM Sparse multicast group table for receivers for the group. If the DR has a
receiver for the group being advertised in the Source Active message, the RP sends a Join message
towards that source.
In Figure 9 , if the MSDP device and RP in domain 4 has a table entry for the receiver, the RP sends
a Join message on behalf of the receiver back through the RPF tree to the source, in this case the
source in domain 1.
Source Active caching is enabled in MSDP on Brocade devices. The RP caches the Source Active
messages it receives even if the RP does not have a receiver for the group. Once a receiver arrives,
the RP can then send a Join to the cached source immediately.
The size of the cache used to store MSDP Source Active messages is 32K.
Configuring MSDP
To configure MSDP, perform the following tasks:
• Enable MSDP.
• Configure the MSDP peers.
NOTE
The PIM Sparse Rendezvous Point (RP) is also an MSDP peer.
NOTE
Devices that run MSDP usually also run BGP. The source address used by the MSDP device is
normally configured to be the same source address used by BGP.
Enabling MSDP
To enable MSDP, enter the following command.
Brocade(config)# router msdp
Syntax: [no] router msdp