Configuring IGMP Querier Parameters

Context

IGMP maintains group memberships using Query and Report messages. When multiple multicast switches exist on a network segment, an IGMP querier is elected to send IGMP Query messages. The IGMP querier can work normally using default settings of querier parameters. You can modify the querier parameters to enable the querier to update group membership efficiently, helping avoiding network congestion.

Table 1 lists descriptions and default settings of IGMP querier parameters.

**Table 1** Descriptions and default settings of IGMP querier parameters
Parameter	Description	Default Setting
General query interval	This parameter specifies the interval for sending IGMP General Query messages. The querier sends IGMP General Query messages at specified intervals to maintain group memberships of interfaces.	60s
Robustness variable of the IGMP querier	This parameter specifies the retransmission count of IGMP packets to minimize the 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 IGMP General Query messages	After a multicast member receives an IGMP General Query message, it must send a Report message to the IGMP querier within the maximum response time.	10s
Other querier present interval	If non-queriers do not receive any Query message within this interval, they consider the querier invalid and trigger election of a new querier.	125s (if the robustness variable, general query interval, and maximum response time are all default values)
Group-specific or group-and-source-specific query interval	This parameter specifies the interval for sending Group-Specific or Group-and-Source-Specific query messages. When the querier receives a Leave message for a group, it sends Group-Specific or Group-and-Source-Specific query messages at specified intervals to check for other members in the group.	1s

If IGMP is enabled on user-side interfaces of multiple devices on a shared network segment, the devices must have the same querier configuration. Otherwise, IGMP may not function normally.

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

Configuration in the IGMP view is valid globally, whereas configuration in the interface view is valid only for the specific interface.
If a querier parameter is configured in both the interface view and IGMP view, configuration in the interface view takes precedence over configuration in the IGMP view. If a querier parameter is not configured on an interface, the interface uses the configuration in the IGMP view.
If non-default configuration is made in the IGMP view, the default configuration in the interface view does not take effect.

Procedure

Configuring global IGMP querier parameters
1. Run system-view
  The system view is displayed.
2. Run igmp [ vpn-instance vpn-instance-name ]
  The IGMP view is displayed.
3. Run timer query interval
  The general query interval is configured.
4. Run robust-count robust-value
  The robustness variable of the IGMP querier is configured.
5. Run max-response-time interval
  The maximum response time for IGMP General Query messages is configured.
6. Run timer other-querier-present interval
  The other querier present interval is configured.
7. Run lastmember-queryinterval interval
  The group-specific or group-and-source-specific query interval is configured.
Ensure that the general query interval is longer than the maximum response time for IGMP Query messages and is shorter than the other querier present interval; otherwise IGMP Report messages may not be sent in response to IGMP Query messages in a timely manner, causing the switch to delete multicast entries.
Configuring IGMP 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 igmp timer query interval
  The general query interval is configured.
5. Run igmp robust-count robust-value
  The robustness variable of the IGMP querier is configured.
6. Run igmp max-response-time interval
  The maximum response time for IGMP General Query messages is configured.
7. Run igmp timer other-querier-present interval
  The other querier present interval is configured.
8. Run igmp lastmember-queryinterval interval
  The group-specific or group-and-source-specific query interval is configured.
Ensure that the general query interval is longer than the maximum response time for IGMP Query messages and is shorter than the other querier present interval; otherwise IGMP Report messages may not be sent in response to IGMP Query messages in a timely manner, causing the switch to delete multicast entries.