Configuration Notes and Limitations for PIM6 SM Snooping

  • PIM6 SM snooping applies only to PIM6 SM.
  • PIM6 SM traffic snooping is supported for both switch and router images.
  • MLD snooping must be enabled on the device that will be running PIM6 SM snooping. The PIM6 SM traffic snooping feature requires MLD snooping.
  • PIMv6 snooping is not supported on default VLANs on router images.
Note: Use the passive mode of MLD snooping instead of the active mode. The passive mode assumes that a router is sending group membership queries as well as join and prune messages on behalf of receivers. The active mode configures the device to send group membership queries.
  • All the device ports connected to the source and receivers or routers must be in the same port-based VLAN.
  • The PIM6 SM snooping feature assumes that the group source and the device are in different subnets and communicate through a router. The source must be in a different IP subnet than the receivers. A PIM6 SM router sends PIM join and prune messages on behalf of a multicast group receiver only when the router and the source are in different subnet. When the receiver and source are in the same subnet, they do not need the router in order to find one another. They find one another directly within the subnet.

The device forwards all IP multicast traffic by default. Once you enable MLD snooping and PIM6 SM traffic snooping, the device initially blocks all PIM6 SM traffic instead of forwarding it. The device forwards PIM6 SM traffic to a receiver only when the device receives a join message from the receiver. Consequently, if the source and the downstream router are in the same subnet, and PIM6 SM traffic snooping is enabled, the device blocks the PIM6 SM traffic and never starts forwarding the traffic. This is because the device never receives a join message from the downstream router for the group. The downstream router and group find each other without a join message because they are in the same subnet.

Note: If the "route-only" feature is enabled on a Layer 3 Switch, PIM6 SM traffic snooping will not be supported.