IGMP defines the procedures that enable an IP end system to notify routers on its LAN that it wants to join or leave a particular IP multicast group.
A router periodically sends an IGMP query asking whether stations want to join (or continue to be part of) a multicast group.
A host that wants to join a group or renew its group membership responds with an IGMP membership report. Membership reports are addressed to the multicast address of the group being joined or renewed.
A router listens for these reports and uses them to determine whether at least one station on the LAN wants to receive traffic sent to that multicast address.
Many switch products enable the switch administrator to turn on IGMP snooping, which causes the switch ...