The Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships.
A network designed to deliver a multicast service using IGMP might use this basic architecture:
A single router per subnet is elected to perform this querying function.
IGMP is vulnerable to some attacks,[2][3][4][5] and firewalls commonly allow the user to disable it if not needed.
[7] IGMPv2, defined in 1997,[8] improves IGMPv1 by adding the ability for a host to signal a desire to leave a multicast group.
In 2002, IGMPv3 improved IGMPv2 by supporting source-specific multicast[9] and introduces membership report aggregation.
A means for routers to select an IGMP querier for the network is introduced.