Configuring MLD Querier Parameters

Context

Multicast Listener Discovery (MLD) Query and Report messages are used to maintain membership. When multiple IPv6 multicast devices exist on a network segment, the MLD querier sends MLD Query messages. The MLD querier uses multiple parameters whose default values can support proper working of the MLD querier. You can modify the querier parameters to enable the querier to update group membership in a timely manner and prevent network congestion.

Table 1 lists the description and default settings of MLD querier parameters.

**Table 1** Description and default settings of MLD querier parameters
Parameter	Description	Default Setting
Interval for sending MLD General Query messages	The querier sends MLD General Query messages at the specified interval to maintain memberships of interfaces. This parameter specifies the interval for sending MLD General Query messages.	125s
Robustness variable of the MLD querier	The robustness variable of the MLD querier specifies the retransmission count of MLD packets to minimize impact of packet loss on the network. The robustness variable defines the following values: Number of times the querier sends General Query messages after startup. Number of times the querier sends Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages after receiving a Done message.	2
Maximum response time for MLD General Query messages	After a multicast member receives an MLD General Query message, it must send a Report message to the MLD querier within the maximum response time.	10s
Other querier present timer	If non-queriers do not receive any Query message within the Keepalive period, they consider the querier invalid and trigger election of a new querier.	If the default values of the robustness variable, interval for sending MLD General Query messages, and maximum response time are used, the other querier present timer value is 255 seconds.
Interval for sending Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages	When the querier receives a Done message that a host sends to leave a multicast group, the querier periodically sends Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages to check for other members in the multicast group. This parameter specifies the interval for sending Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages.	1s

The MLD querier parameters can be configured in the MLD view or interface view.

The configuration in the MLD view is globally valid, whereas the configuration in the interface view takes effect only for the specified interface.
If a querier parameter is configured in the interface view and the MLD view, the configuration in the interface view takes effect. If a querier parameter is not configured on an interface, the interface uses the configuration in the MLD view.
If non-default configuration is performed in the MLD view, the default configuration in the interface view does not take effect.

Procedure

Configuring global MLD querier parameters
1. Run system-view
  The system view is displayed.
2. Run mld
  The MLD view is displayed.
3. Run timer query interval
  The interval for sending MLD General Query messages is set on the device.
4. Run robust-count robust-value
  The robustness variable of the MLD querier is set.
5. Run max-response-time interval
  The maximum response time for MLD General Query messages is set.
6. Run timer other-querier-present interval
  The other querier present timer is configured.
7. Run lastlistener-queryinterval interval
  The interval for sending Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages is set.
During MLD querier configuration, ensure that the interval for sending General Query messages is larger than the maximum response time for MLD Query messages and is smaller than the other querier present timer.
Configuring MLD querier parameters on an interface
1. Run system-view
  The system view is displayed.
2. Run interface interface-type interface-number
  The interface view is displayed.
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
  
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
4. Run mld timer query interval
  The interval for sending MLD General Query messages is set on the interface.
5. Run mld robust-count robust-value
  The robustness variable of the MLD querier is set.
6. Run mld max-response-time interval
  The maximum response time for MLD General Query messages is set.
7. Run mld timer other-querier-present interval
  The other querier present timer is configured.
8. Run mld lastlistener-queryinterval interval
  The interval for sending Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages is set.