Internet Core Protocols: The Definitive Guide

IGMP Message Types

There are only four IGMP messages defined in RFC 2236, two of which were previously defined for IGMPv1. The message types are listed in Table 4.5.

Table 4.5. IGMP Message Types and Their Meanings

Message Type	Description
Membership Query	Used by IGMPv1 and IGMPv2 multicast routers to locate the multicast groups in use by hosts on the local network.
v1 Membership Report	Identifies this message as an IGMPv1 Membership Report.
v2 Membership Report	Identifies this message as an IGMPv2 Membership Report.
v2 Leave Report	Used by IGMPv2 hosts to announce that they are leaving a multicast group.

For detailed information about each of these message types, refer to the sections that follow.