Source Active Caching

When an MSDP device that is also an RP receives a Source Active message, it checks the PIM sparse multicast group table for receivers for that group. If there are receivers for that group being advertised in the Source Active message, the RP sends a Join message towards the source.

In PIM Sparse Domains Joined by MSDP Devices, 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 RUCKUS 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 4K. MSDP SA cache size can be configured using the system-max msdp-sa-cache command.