31.4.2 IP address control method

(a) Registering Entries

When an MLDv1 Report message or MLDv2 Report (membership request) message is received, the multicast IP address is learned from the multicast group address included in the message, and an entry is created that forwards traffic bound for the multicast group only to ports for which MLDv1 or MLDv2 Report messages were received.

(b) Deleting an entry

Learned multicast IP addresses are deleted in any of the following cases when group members no longer exist on all ports:

• An MLDv1 Done message is received.

  Group-Specific Query messages are sent from the Switch to the port that received MLDv1 Done messages, twice every second (Group-Specific Query messages are only sent when the Switch is the representative querier). If there is no response, only that port is deleted from the entries (forwarding of multicast traffic to this port is suppressed). If no group members are left in all ports in the VLAN, the entry itself is deleted.

• An MLDv2 Report (leave request) message is received.

  When an MLDv2 Report (leave request) message whose multicast address record type is CHANGE_TO_INCLUDE_MODE is received, Group-Specific Query messages are sent from the Switch to the port that received the message, twice every second (Group-Specific Query messages are only sent when the Switch is the representative querier). If there is no response, only that port is deleted from the entries. If no group members are left in all ports in the VLAN, the entry itself is deleted. When an MLDv2 Report message whose multicast address record type is BLOCK_OLD_SOURCES is received, Group-and-Source-Specific Query messages are sent from the Switch, twice every second (Group-and-Source-Specific Query messages are only sent when the Switch is the representative querier). Entries are deleted on timeout regardless of the response to Group-Source-and-Specific Query messages.

  Notes

  The timeout period is Multicast Listener Interval period.

• A set time elapses after an MLDv1 or MLDv2 Report (membership request) message is received.

  Multicast routers periodically send MLD Query messaging to verify that group members exist on directly connected interfaces. When the Switch receives an MLD Query message from a router, it forwards it to all ports in the VLAN. If there is no response to the MLD Query message, only that port is deleted from the entries. When no response is received from any port, the entry itself is deleted.

  If the Switch does not receive Multicast Listener Interval times or MLDv1/MLDv2 Report messages, the corresponding entries are deleted.

  Notes

  Multicast Listener Interval is calculated in Robustness Variable(RV)NGQuery Interval(QI)+Query Response Interval(QRI).

  RV,QI,QRI is shown below.

  .When another device is operating in MLDv2 with a representative querier

  RV,QI = retrieve from received Query messaging

  QRI=10 seconds

  .When the Switch operates in MLDv2 with a representative querier or in MLDv1

  RV=2

  QI = Query Interval set for the local switch (configuration command ipv6 mld query-)

  Setting of interval.) 125 seconds if not set.

  QRI=10 seconds