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When used as a Layer 2 switch, the 1424T supports IGMPv1 and IGMPv2 to prune group membership per port within a VLAN. This feature is called IGMP snoop and it allows you to optimize the multicast data flow for a group within a VLAN to only those ports that are members of the group.
The switch builds a database of group members by listening to IGMP reports from each port. It suppresses the reports heard by not forwarding them out to ports other than the one receiving the report, forcing the members to continuously send their own reports. The switch relays group membership from the hosts to the multicast routers. It forwards queries from multicast routers to all port members of the VLAN. Furthermore, it forwards multicast data only to the participating group members and to the multicast routers within the VLAN.