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IGMP Overview

The IPv4 address scheme assigns class D addresses for IP multicast. IGMP is the protocol that uses these addresses, which can be in the range 224.0.0.0 to 239.255.255.255. The following addresses have specific functions or are unavailable:

224.0.0.0 is reserved—you cannot assign it to a group.
224.0.0.1 is the all-hosts address—a packet sent to this address reaches all hosts on a subnet.
224.0.0.2 is the all-routers address—a packet sent to this address reaches all routers on a subnet.

This implementation of IGMP complies with IGMP versions 1, 2, and 3. IGMPv3 supports source-specific join and leave messages and is backward compatible with IGMPv1 and IGMPv2.

IGMPv2 mode interfaces exchange the following types of messages between routers and hosts:

Group membership queries
Group membership reports
Leave group membership messages

IGMPv3 mode interfaces exchange the following types of messages with IGMPv3 hosts:

Group membership queries
IGMPv3 group membership reports

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