The PIM snooping feature for IPv4 is supported in the PBB I-VPLS context to provide efficient multicast replication in the customer domain. This is similar to PIM snooping for IPv4 in a regular VPLS with the difference being the handling of PIM messages arriving from the B-VPLS side over a B-VPLS SAP or SDP.
The first PIM join message received over the local B-VPLS adds all the B-VPLS SAP and SDP components into the related multicast table associated with the I-VPLS context, and the multicast for the join is flooded throughout the B-VPLS. This is in line with the PBB model, where the B-VPLS infrastructure emulates a backbone LAN to which every I-VPLS is connected by one virtual link.
When a neighbor is located on a remote I-VPLS instance over the B-VPLS infrastructure, its location is identified by the B-VPLS SDP and SAP on which the hello message was received. The neighbor is also identified by the source B-MAC address used in the PBB header of the hello message. This is the B-MAC associated with the B-VPLS instance on the remote PBB PE.
PIM snooping for IPv4 in an I-VPLS is not supported with the following forms of default SAP:
:*
*.null
*.*