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Configuring IP Multicast Routing
Configuring Optional IGMP Features
The following example shows how to configure the switch to wait 250 seconds from the time it received the last query
until the time that it triggers the IGMP election process. When the timeout value is explicitly configured, the query interval
does not automatically adjust. Because the query interval was not explicitly configured to change the default value (60
seconds), the default timeout period of two times the query interval, or 120 seconds, is overridden by the specified value.
interface GigabitEthernet0/1
ip igmp querier-timeout 250
Changing the IGMP Query Timeout for IGMPv2
If you are using IGMPv2, you can specify the period of time before the switch takes over as the querier for the interface.
By default, the switch waits twice the query interval controlled by the ip igmp query-interval interface configuration
command. After that time, if the switch has received no queries, it becomes the querier.
You can configure the query interval by entering the show ip igmp interface interface-id privileged EXEC command. This
procedure is optional.
BEFORE YOU BEGIN
We recommend that you do not modify the IGMP query interval and IGMP querier timeout values. However, if you
configure the appropriate commands to change the query interval and querier timeout default values, the following
conditions apply:
If you use the ip igmp query-interval command to configure the query interval, the timeout value is automatically
adjusted to two times the query interval; the adjusted timeout value, however, is not reflected in the interface
configuration.
Note:
To confirm that the timeout value adjusted to two times the modified query interval, use the show ip igmp interface
command to display the query interval and timeout values being used for the interface.
Conversely, if you use the ip igmp querier-timeout command to configure the timeout value, the query interval does
not automatically adjust to half of the modified timeout value, so it is possible to override the default timeout period
of two times the query interval. If you must configure the timeout period, we recommend that you configure the
timeout value in proportion to the query interval value.
The query interval must be greater than the IGMP maximum query response time. Use the ip igmp
query-max-response-time command to change the maximum query response time value from the default (10
seconds) to a specified length of time, if required.
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