15.2.2 IGMP operation

The following explains IGMPv2 operation using IGMPv2 messages:

• IPv4 multicast routers obtain information about IPv4 multicast membership by regularly sending Multicast Membership Query (General Query) messages on directly connected interfaces to all multicast hosts at 224.0.0.1. For an interface for which multihoming is set, the Switch sends Multicast Membership Query messages to the representative querier's network.

• When a host receives a Multicast Membership Query, it sends a Multicast Membership Report to the corresponding group to report the join status to the group.

• When a Multicast Membership Report is received from a host, the IPv4 multicast router adds the group to the membership list.

• When a Multicast Leave Group message is received, the group is deleted from the membership list.

The following figure shows how IGMPv2 groups are joined and left.

Figure 15-3: Participating and leaving IGMPv2 groups

The following describes IGMPv3 operation using IGMPv3 messages:

• IPv4 multicast routers obtain information about IPv4 multicast membership by regularly sending Version 3 Multicast Membership Query (General Query) messages on directly connected interfaces to all multicast hosts at 224.0.0.1. For an interface for which multihoming is set, the Switch sends Version 3 Multicast Membership Query messages to the representative querier's network.

• When a host receives a Version 3 Multicast Membership Query, it sends a Version 3 Multicast Membership Report (Current State Report) to 224.0.0.22 to report the join status to the group.

• When an IPv4 multicast router receives a Version 3 Multicast Membership Report (State Change Report) message from a host, it adds or removes the group from membership based on the Group Record type.

The following figure shows how IGMPv3 Report messages are sent from hosts.

Figure 15-4: IGMPv3 Join/Leave Operation