VPLS is a Layer 2 service; therefore, multicast and broadcast frames are normally flooded in a VPLS. Broadcast frames are targeted to all receivers. However, for IP multicast, normally for a multicast group, only some receivers in the VPLS are interested. Flooding to all sites can cause wasted network bandwidth and unnecessary replication on the ingress PE router.
To avoid this condition, VPLS is IP multicast-aware; therefore, it forwards IP multicast traffic based on multicast states to the object on which the IP multicast traffic is requested. This is achieved by enabling the following related IP multicast protocol snooping:
IGMP snooping
MLD snooping
PIM snooping