IGMP Snooping in a Multicast Router

IGMP (Internet Group Management Protocol) snooping is a Layer 2 feature and is achieved by using the Layer 2 multicast forwarding table. However when multicast routing is enabled on a 200 Series switch, Layer 2 multicast forwarding entries do not affect multicast data forwarding. Instead, corresponding IP multicast table entries need to be created to achieve similar behavior.

On a multicast router, for IGMP snooping to be functional, any multicast routing protocol needs to be operationally enabled on the routing interface. IGMP snooping also needs to be enabled on the VLAN corresponding to the routing interface. Note that IGMP snooping behavior will not be functional on VLANs that are not enabled for VLAN routing.