Multicast Source Discovery Protocol (MSDP)

The Multicast Source Discovery Protocol (MSDP) describes a mechanism to connect multiple IP Version 4 Protocol Independent Multicast Sparse-Mode (PIM-SM) domains together. Each PIM-SM domain uses its own independent Rendezvous Point (RP) and does not have to depend on RPs in other domains. When an RP in a PIM-SM domain first learns of a new sender, e.g., via PIM register messages, it constructs a “Source-Active” (SA) message and sends it to its MSDP peers. The SA message contains the following fields:

  • The source address of the data source.
  • The group address the data source sends to.
  • The IP address of the RP.

–rfc3618

Configuration Commands

MSDP is typically run on an IP address bound to a loopback interface. In order for two devices to establish an MSDP neighbor relationship, L3 connectivity must already be established.

switch(config)# router msdp
switch(config-msdp)# enable
switch(config-msdp)# ip msdp peer <IP>
switch(config-msdp-peer)# enable
switch(config-msdp-peer)# connect-source <IFNAME>

Show commands to validate functionality:

show ip msdp peer
show ip msdp count
show ip msdp sa-cache

Test Steps

  1. Configure a loopback interface on both 8325 that are acting as core devices.
  2. Enable PIM on loopback interface
  3. Configure MSDP and create a peer relationship between 8325’s using a loopback as the source.

Expected Results

Verify MSDP session is up and it is using loopback interface as source.

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