(Optional) Configuring the MLD Snooping Querier
Context
When Multicast Listener Discovery (MLD) snooping is enabled on a Layer 2 device, the Layer 2 device can listen on MLD protocol packets exchanged between an MLD querier and user hosts to dynamically create Layer 2 multicast forwarding entries and provide Layer 2 multicast functions.
A Layer 2 device cannot create Layer 2 multicast forwarding entries by listening on MLD protocol packets in the following conditions, even when MLD snooping is enabled on the device:
The interfaces on the upstream Layer 3 multicast device have static multicast groups configured and do not run the MLD protocol.
The multicast source is located on the same Layer 2 network as user hosts, and therefore no Layer 3 multicast device is required.
In either of the preceding conditions, you can configure the MLD snooping querier on the Layer 2 multicast device. Then the Layer 2 multicast device substitutes for a Layer 3 multicast device to send MLD Query messages to user hosts.
Procedure
- Run system-view
The system view is displayed.
- Run vlan vlan-id
The VLAN view is displayed.
- Run mld-snooping querier enable
The MLD snooping querier is enabled.
After MLD snooping querier is enabled, the router periodically broadcasts MLD Query messages to all the interfaces in a VLAN, including the router ports. This may result in MLD querier reelection if an MLD querier already exists on the multicast network. If an MLD querier already exists on the multicast network, configuring MLD snooping querier is not recommended. If MLD snooping querier needs to be configured in this condition, ensure that the router has a larger IPv6 address than the upstream MLD querier.
- (Optional) Set the querier parameters.
Ensure that the interval for sending MLD General Query messages is longer than the maximum response time for MLD Query messages.
Querier Parameter
Configuration Command
Description
Default Setting
Version
Interval for sending MLD General Query messages
mld-snooping query-interval query-interval
The querier sends MLD General Query messages at the specified interval to maintain memberships in a VLAN.
60 seconds
MLDv1, MLDv2
MLD robustness variable
mld-snooping robust-count robust-count
The robustness variable defines the following values:- Number of times the querier sends General Query messages after startup. The packet sending interval is 1/4 of the configured interval for sending General Query messages.
- Number of times the querier sends Group-Specific Query messages after receiving a Done message. The packet sending interval is the same as the configured interval for sending Group-Specific Query messages.
2
MLDv1, MLDv2
Maximum response time for MLD Query messages
mld-snooping max-response-time max-response-time
After receiving an MLD Report message, the router sets the aging time of member port to: Interval for sending General-Query messages x MLD robustness variable + Maximum response time.
After a multicast member receives an MLD Query message, it must send a Report message within the maximum response time.
10 seconds
MLDv2
Interval for sending Last Member Query messages
mld-snooping last-listener-query-interval query-interval
When receiving a Done message from a user host, the router sets the aging time of member port to: Interval for sending Group-Specific messages x MLD robustness variable. That is, the router continuously sends Group-Specific messages for "MLD robustness variable" times. This parameter specifies the interval for sending Last Member Query messages.
1 second
MLDv2
- (Optional) Run quit
Return to the system view.
- (Optional) Run mld-snooping send-query source-address ipv6-address
The source IPv6 address of the MLD General Query message is configured.
By default, the source IPv6 address of MLD General Query messages on an MLD querier is FE80::. If the specified address is being used by another device on the network, run this command to change the source IPv6 address.
