IGMP snooping on pseudowires

You can prevent multicast traffic from traversing a pseudowire (to egress PE routers) unless there are IGMP receivers for the traffic. The default IGMP snooping implementation for a VPLS instance adds each pseudowire interface to its oif list. This includes traffic sent from the ingress PE router to the egress PE router regardless of interest. The snoop-pseudowires option prevents multicast traffic from traversing the pseudowire (to the egress PE routers) unless there are IGMP receivers for the traffic. In other words, multicast traffic is forwarded only to VPLS core interfaces that are either router interfaces or IGMP receivers. In addition to the benefit of sending traffic to interested PE routers only, snoop-pseudowires optimizes a common path between PE-P routers wherever possible. Thus, if two PE routers connect using through the same P router, only one copy of the packet is sent because the packet is replicated on only those P routers for which the path is divergent.