2-12
It is meaningless to configure an IGMP Snooping querier in a multicast network running IGMP.
Although an IGMP Snooping querier does not take part in IGMP querier elections, it may affect IGMP
querier elections because it sends IGMP general queries with a low source IP address.
Configuring IGMP Queries and Responses
You can tune the IGMP general query interval based on actual condition of the network.
Upon receiving an IGMP query (general query or group-specific query), a host starts a timer for each
multicast group it has joined. This timer is initialized to a random value in the range of 0 to the
maximum response time (the host obtains the value of the maximum response time from the Max
Response Time field in the IGMP query it received). When the timer value comes down to 0, the host
sends an IGMP report to the corresponding multicast group.
An appropriate setting of the maximum response time for IGMP queries allows hosts to respond to
queries quickly and avoids bursts of IGMP traffic on the network caused by reports simultaneously sent
by a large number of hosts when the corresponding timers expire simultaneously.
z
For IGMP general queries, you can configure the maximum response time to fill their Max
Response time field.
z
For IGMP group-specific queries, you can configure the IGMP last-member query interval to fill
their Max Response time field. Namely, for IGMP group-specific queries, the maximum response
time equals to the IGMP last-member query interval.
Configuring IGMP queries and responses globally
Follow these steps to configure IGMP queries and responses globally:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Enter IGMP Snooping view
igmp-snooping
—
Configure the maximum
response time to IGMP general
queries
max-response-time interval
Optional
10 seconds by default
Configure the IGMP
last-member query interval
last-member-query-interval
interval
Optional
1 second by default
Configuring IGMP queries and responses in a VLAN
Follow these steps to configure IGMP queries and responses in a VLAN:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Enter VLAN view
vlan vlan-id
—
Configure IGMP general query
interval
igmp-snooping query-interval
interval
Optional
60 seconds by default