(Optional) Configuring the MLD Snooping Querier
Context
When MLD snooping is enabled on a Layer 2 device, the device can listen to 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.
Even with MLD snooping enabled, a Layer 2 device cannot create Layer 2 multicast forwarding entries by listening to MLD protocol packets in the following conditions:
Interfaces on the upstream Layer 3 multicast device are statically bound to multicast groups and do not run the MLD protocol.
The multicast source is located on the same Layer 2 network as user hosts, and no Layer 3 multicast device is required.
In the preceding scenarios, configuring the Layer 2 multicast device as an MLD snooping querier enables the device to send MLD Query messages to user hosts in place of a Layer 3 multicast device.
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.
If an IPv6 Layer 3 multicast function (such as MLD or IPv6 PIM) is enabled on a VLANIF interface, the MLD snooping querier cannot be enabled in the corresponding VLAN.
After MLD snooping querier is enabled in a VLAN, the switch periodically broadcasts MLD Query messages to all the interfaces in the VLAN, including the router ports. If an MLD querier already exists on the multicast network, configuring MLD snooping querier is not recommended because this may result in MLD querier reelection. If MLD snooping querier needs to be configured in this condition, ensure that the switch has a larger IP address than the upstream MLD querier.
MLD snooping querier and MLD snooping proxy cannot be enabled simultaneously in the same VLAN.
If multicast VLAN replication is configured, the MLD snooping querier function cannot be enabled in user VLANs.
- (Optional) Set the querier parameters.
Ensure that the interval of MLD General Query messages is longer than the maximum response time for MLD Query messages.
Querier Parameter
Configuration Command
Description
Default Setting
Version
Interval of MLD General Query messages
mld-snooping query-interval query-interval
The querier sends MLD General Query messages at the specified interval to maintain group memberships in a VLAN.
125 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 switch sets the aging time of member port to: (Interval for sending General-Query messages x MLD robustness variable + Maximum response time).
After a group member receives an MLD Query message, it must send a Report message within the maximum response time.
10 seconds
MLDv2
Interval of Last Member Query messages
mld-snooping last-listener-query-interval query-interval
When receiving a Done message from a user host, the switch sets the aging time of member port to: (Interval for sending Group-Specific messages x MLD robustness variable.) The switch continuously sends Group-Specific messages for "MLD robustness variable" times. This parameter specifies the interval at which the switch sends 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, an MLD querier uses FE80:: as the source IPv6 address of MLD General Query messages. If another device on the network is using the default source address, run this command to change the source IPv6 address.