31.3.3 Connection with the multicast router
In addition to the hosts that have already joined a group, the forwarding destinations for multicast packets also include neighboring multicast routers. When the Switch and a multicast router are connected and IGMP snooping is used, the port connected to the multicast router to forward multicast packets to the router (abbreviated hereafter to multicast router port) can be specified by configuration.
The Switch forwards all multicast packets to the specified multicast router port.
Also, because IGMP is a protocol for sending and reception between router hosts, IGMP messages are accepted by routers and hosts. The Switch forwards IGMP messages as shown in the following table.
|
IGMP message type |
Transfer port within the VLAN |
Remarks |
|---|---|---|
|
Membership Query |
Forwarded to all ports. |
|
|
Version 2 Membership Report |
Forwarded only to multicast router ports. |
|
|
Leave Group |
Not forwarded to any port when group members still exist for other ports. Forwarded to multicast router ports when no group members exist for other ports. |
# |
|
Version 1 Membership Report |
Forwarded only to multicast router ports. |
- #
-
Relay operation is performed when a querier is set for the local device and another device is a representative querier. If the local device is a representative querier, IGMPv2 Leave messaging is not forwarded. If no querier has been set, forwarding is always performed to multicast router ports. However, if a port that has not received an IGMPv1, IGMPv2, or IGMPv3 Report (membership request) message receives an IGMPv2 Leave message, the IGMPv2 Leave message is not forwarded regardless of the querier settings.
|
IGMPv3 message type |
Transfer port within the VLAN |
Remarks |
|
|---|---|---|---|
|
Version3 Membership Query |
Forwarded to all ports. |
||
|
Version 3 Membership Report |
Membership Request Report |
Forwarded only to multicast router ports. |
|
|
Leave Request Report |
Not forwarded to any port when group members still exist for other ports. Forwarded to multicast router ports when no group members exist for other ports. |
# |
|
- #
-
Relay operation is performed when a querier is set for the local device and another device is a representative querier. If the local device is a representative querier, IGMPv3 Report (detachment req) messageis not forwarded. If no querier has been set, forwarding is always performed to multicast router ports. However, if a port that has not received an IGMPv1, IGMPv2, or IGMPv3 Report (membership request) message receives an IGMPv3 Report (leave request) message, the IGMPv3 Report (leave request) message is not forwarded regardless of the querier settings.