IGMP snooping

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IGMP snooping is the process of listening to Internet Group Management Protocol (IGMP) network traffic to control delivery of IP multicasts. Network switches with IGMP snooping listen in on the IGMP conversation between hosts and routers and maintain a map of which links need which IP multicast transmission. Multicasts may be filtered from the links which do not need them, conserving bandwidth on those links.

IGMP snooping is described in an informational IETF RFC but affects bridging operations, the purview of the IEEE. Because of a lack of an authoritative standard, the process may operate differently on different equipment.