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24 Description of IGMP Snooping and MLD Snooping
Table 24-5 Operation for each MLDv2 message
MLDv2 message type
Version2 Multicast Listener Query
Version2
Multicast
Listener Report
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This is the forwarding operation when a querier is set for the local device. If no
querier has been set, forwarding is always performed to multicast router ports.
However, if a port that has not received an MLDv1 or MLDv2 Report (membership
request) message receives an MLDv2 Report (detachment request) message, the
MLDv2 Report (detachment request) message is not forwarded regardless of the
querier settings.
24.4.3 MLD querier functionality
The MLD querier functionality is used by the Switch to send MLD Query messages by
proxy to recipient hosts on environments where no multicast router exists in the VLAN, and
only hosts that send and receive multicast packets exist. Multicast routers regularly send
MLD Query messages and then check for reception from hosts to determine whether group
members exist. If no multicast router exists, group members can no longer be monitored
because no response is received from recipient hosts. This functionality enables the MLD
snooping functionality even when no multicast routers exist in the VLAN. The Switch sends
an MLD Query message every 125 seconds.
In order to use the MLD querier functionality, the source IP address of the MLD Query
message must be set for VLANs using the MLD snooping functionality.
When devices sending MLD Query messages exist in a VLAN, the MLD Query message
transmission source with the lowest IP address becomes the representative querier, and it
sends MLD Query messages. If another device in the VLAN is the representative querier,
the Switch stops using the MLD querier functionality to send Query messages.
If the representative querier stops, such as due to a malfunction, a new representative
querier is chosen. When the Switch is determined to be the representative querier, such as
due to a malfunction on another device in the VLAN, MLD Query message transmission is
started. The monitoring time for representative queriers on the Switch is 255 seconds.
By default, the version for MLD Queries sent by the Switch is MLDv1. Once the device is
running, the MLD Query version follows the MLD version of the representative querier.
442
Membership Request
Report
Detachment Request
Report
Transfer port within the VLAN
Forwarded to all ports.
Forwarded only to multicast router ports.
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.
Rema
rks
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