15.2.4 Managing Group Members

(1) Managing IPv4 Group Members When Using IGMPv2

Group members are registered when a Membership Report is received from a host. Non-Queriers are also registered as group members as with Queriers when a Membership Report is received from a host.

When a Querier receives a Leave Group message reporting that a host is leaving a group, it checks for the existence of other hosts that have joined the group member receiving the departure report. The Querier does this by sending continuous Membership Query (Group-Specific Query) messages to the corresponding group every second. After these messages are sent twice, if no Membership Report is received within 1 second, the corresponding group is deleted. Note that Leave Group messages are disregarded by Non-Queriers.

If a Leave Group message is received on an interface that is configured for multihoming, Membership Query message is sent to all networks that are configured for the interface, regardless of Querier,Non-Querier.

(2) Managing IPv4 Group Members When Using IGMPv3

The following explains IPv4 group member registration and deletion for when IGMPv3 is used.

When a host sends a Report message indicating a request to join a multicast group and a router receives the message, the router registers group information This group information consists of a group address and the source address to the group address. Both the Querier and Non-Querier routers can perform this registration.

When the Querier receives a Report message indicating a leave request from a multicast group, the Querier checks for the existence of other hosts that have joined the group member by sending a message every second indicating the following, based on whether a sender list is specified.

• If no sender list is specified: Group-Specific Query message

• If a sender list is specified: Group-and-Source-Specific Query message

If the Switch is the Querier, after these messages are sent twice, if no Report is received within one second, the corresponding group information is deleted. If the Switch is a Non-Querier, corresponding group information is deleted after a message is received from the Querier.

When a Report indicating a detachment request from a multicast group is received on an interface for which multihoming is set, a Group-Specific Query message or Group-and-Source-Specific Query message is sent to all networks configured on the interface regardless of Querier,Non-Querier.