Configuring General IGMP Snooping Parameters

You can configure a number of general interval parameters that apply to all IGMP snooping interfaces. You can also configure these parameters to apply to a particular VLAN.

You can configure three intervals to determine the host-query message parameters used to time out a group:

• Query interval
• Query last-member interval
• Query response interval

To configure time-out group intervals, include the query-interval statement:

By default, the query interval is 125 seconds. You can configure any value in the range 1 through 1024 seconds.

The last-member query interval is the maximum amount of time between group-specific query messages, including those sent in response to leave-group messages. You can lower this interval to reduce the amount of time it takes to detect the loss of the last member of a group. To configure the maximum amount of time between group-specific query messages, include the query-last-member-interval statement:

By default, the last-member query interval is 1 second. You can configure any value in the range 0.1 through 0.9 seconds, and then 1-second intervals from 1 through 1024 seconds.

To configure how long the router waits to receives a response from its host-query messages, include the query-response-interval statement:

By default, the query response interval is 10 seconds. You can configure any value in the range 1 through 1024 seconds. However, this interval must be less than the interval set in the query-interval statement.

In addition to the intervals, the IGMP robustness variable provides fine-tuning to allow for expected packet loss on a subnet. It is basically the number of intervals to wait before timing out a group. You can wait more intervals if subnet packet loss is high and IGMP report messages might be lost. To configure a robustness variable, include the robust-count statement:

By default, the robust count is 2. You can configure any value in the range 2 through 10 intervals.

You can configure general IGMP snooping statements at the following hierarchy levels:

• [edit bridge-domains bridge-domain-name protocols igmp-snooping]
• [edit bridge-domains bridge-domain-name protocols igmp-snooping vlan vlan-id]
• [edit routing-instances routing-instance-name bridge-domains bridge-domain-name protocols igmp-snooping]
• [edit routing-instances routing-instance-name bridge-domains bridge-domain-name protocols igmp-snooping vlan vlan-id]