/mcpDestination IP: GDA G IGMP Packet IGMP data contains, furthermore, the GDA and some other fields. G Host membership queries are sent by the router to the all-multicast address: 224.0.0.1. These queries use 0.0.0.0 in the IGMP GDA field. A host for each group must respond to that query, or the router stops forwarding the traffic for that GDA to that segment (after three attempts). The router keeps a multicast routing entry for each source, and links it to a list of outgoing interfaces (interface from where the IGMP report came). After three IGMP query attempts with no answer, this interface is erased from the outgoing interface list for all entries linked to that GDA. Note: IGMPv1 has no leave mechanism. If a host no longer wants to receive the traffic, it simply quits. If it is the last host on the subnet, the router does not receive any answer to its query, and deletes the GDA for that subnet. IGMPv2 In IGMP Version 2 (IGMPv2), the version field has been removed, and the type field can now accept different values. The types are shown below. Membership Query G IGMPv1 Membership Report G Version 2 Membership Report G Leave Group G Descriptions of the most important new features added in IGMPv2 are listed below. IGMP Leave Message: when a host wants to leave a group, it should send a Leave Group IGMP message to destination 224.0.0.2 (instead of leaving silently like in IGMPv1). G A router can now send a group-specific query by sending a Membership Query to the group GDA instead of sending it to 0.0.0.0. G IGMPv3 In IGMP Version 3 (ICMPv3), there is a type field that can have the following values: Membership query G Version 3 Membership Report G An implementation of IGMPv3 must also support the following three message types, for interoperation with previous versions of IGMP: Version 1 Membership Report [RFC1112] G Version 2 Membership Report [RFC2236] G Version 2 Leave Group [RFC2236] G IGMPv3 adds support for source filtering, that is, the ability for a system to report interest in receiving packets from specific source addresses, or from all but specific source addresses sent to a specific multicast address. This feature is also called Source Specific Multicast (SSM).