32.4.4 MLD querier function

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.

Notes

When operating in MLDv1, Query Interval must be 125 seconds for the applicable VLAN.

To use MLD Querier function, you must set the source IP of MLD Query messaging VLAN using MLD snooping function.

There are two ways to set IP addressused by MLD querier facility:

• Set IP as IPv6 interfaces

• Use the configuration command ipv6 mld snooping querier to set the source IP of MLD Query messaging.

If both are set, IP addressset as IPv6 interface takes precedence.

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. In the Switch, the monitoring period for the representative querier follows Other Querier Present Interval.

Notes

Other Querier Present Interval is calculated as Robustness Variable(RV)NGQuery Interval(QI)+Query Response Interval(QRI)/2.

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=125 seconds

QRI=10 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.