Internet Group Management Protocol
Internet Group Management Protocol (IGMP) is a communications protocol that enables a node (receiver) to inform a multicast router (IGMP querier) of the node’s intention to receive particular multicast traffic.
- Routers ask nodes if they need a particular multicast stream (IGMP query).
- Nodes respond to the router if they are seeking a particular multicast stream (IGMP reports).
The IGMP communication protocol is used by the nodes and the adjacent routers on IP networks to interact and to establish ground rules for multicast communication and establish multicast group membership.
IGMP snooping
IGMP snooping is an activity performed by switches to track the IGMP communications related packet exchanges and adapt to filtering the multicast packets. Switches featuring IGMP snooping derive useful information by observing these IGMP transactions between the nodes and routers. This function enables the switches to correctly forward the multicast packets, when needed, to the next switch in the network path.
Switches monitor the IGMP traffic and only send out multicast packets when necessary. A switch typically builds an IGMP snooping table that has a list of all the ports that have requested a particular multicast group. The IGMP snooping table is used to allow multicast packets to travel across the network or to disallow them from traveling across the network. You can configure your switch to avoid IGMP snooping.