Configuring the Querier Function

The querier function enables a device to send Query messages for its upstream device and respond to Multicast Listener Discovery (MLD) messages sent from downstream devices.

Context

There is an MLD-capable Layer 3 multicast device acting as a querier on a multicast network. The querier sends MLD Query messages to create and maintain multicast forwarding entries for normal multicast data forwarding.

The querier function, however, cannot be implemented on a Layer 3 device in either of the following conditions:

MLD messages sent from the Layer 3 device cannot reach a downstream Layer 2 device.
Multicast forwarding entries on the Layer 3 device are statically configured and do not need to be dynamically learned.

In this case, the IGMP querier function of the upstream device cannot be implemented on the network.

To solve these issues, configure the querier function on the Layer 2 device so that it can create and maintain multicast forwarding entries at the data link layer, ensuring normal multicast data forwarding. The querier parameters can be set as required.

Procedure

Run system-view
The system view is displayed.
Perform either of the following operations based on the VLAN or VPLS networking scenario:
- Run the vlan vlan-id command to enter the VLAN view.
- Run the vsi vsi-name [ static ] command to enter the VSI view.
Run mld-snooping enable
MLD snooping is enabled for the VLAN or VSI.
Run mld-snooping querier enable
The querier function is enabled.
(Optional) Run mld-snooping querier-election
The querier election function is enabled, so that the device can participate in querier election.

If the querier function is enabled on multiple devices in a VSI or VLAN, querier election needs to be enabled. The elected querier is used to send Query messages to user hosts.
(Optional) Set querier parameters.
- Run mld-snooping query-interval query-interval
  
  The interval at which a querier sends general Query messages is set.
- Run mld-snooping robust-count robust-count
  
  The number of group-specific Query messages to be sent is set.
- Run mld-snooping max-response-time max-response-time
  
  The maximum time for a querier to wait for responses from downstream hosts is set.
  
  The maximum wait time must be shorter than the interval at which general Query messages are sent.
- Run mld-snooping lastmember-queryinterval lastmember-queryinterval
  
  The interval at which a querier sends group-specific Query messages or source-and group-specific Query messages is set.
In the VSI scenario, if MLD Snooping Proxy is configured on one end of the PW tunnel, you need to configure the IPv6 addresses on the same network segment on the physical interfaces to which the two PW interfaces are iterated. Otherwise, the sending of group-specific query packets is affected.
Run commit
The configuration is committed.