31.2.4 Managing IPv6 Group Members

(1) Managing IPv6 Group Members When Using MLDv1

This section explains the registration and removal of IPv6 group members when the MLDv1 protocol is used.

When a router receives a Multicast Listener Report message from a host, the router registers the host as an IPv6 group member. Both the Querier and Non-Querier routers can perform this registration.

If the Querier receives a Multicast Listener Done message that reports that the host is leaving an IPv6 group, the Querier checks whether any other hosts remain in the group. The Querier does this by sending continuous Multicast Listener Query (Group-Specific Query) messages to the relevant group every second. After the Querier sends a Multicast Listener Query (Group-Specific Query) message twice, if a Multicast Listener Report message is not returned within one second, the Querier deletes the relevant group. Non-Queriers ignore the Multicast Listener Done message and receive the Multicast Listener Query (Group-Specific Query) message sent by the Querier twice and deletes the target group if it does not receive Multicast Listener Report within one second.

(2) Managing IPv6 Group Members When Using MLDv2

The following explains IPv6 group member registration and deletion when MLDv2 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 that consists of the group address and the sender 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: Multicast Address Specific Query message

• If a sender list is specified: Multicast Address 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.