Configuring Igmp Queries And Responses - 3Com 4510G Configuration Manual

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.
For IGMP general queries, you can configure the maximum response time to fill their Max
Response time field.
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...
Enter system view
Enter IGMP Snooping view
Configure the maximum
response time to IGMP general
queries
Configure the IGMP
last-member query interval
Configuring IGMP queries and responses in a VLAN
Follow these steps to configure IGMP queries and responses in a VLAN:
To do...
Enter system view
Enter VLAN view
Configure IGMP general query
interval
Use the command...
system-view
igmp-snooping
max-response-time interval
last-member-query-interval interval
Use the command...
system-view
vlan vlan-id
igmp-snooping query-interval
interval
2-12
Remarks
—
—
Optional
10 seconds by default
Optional
1 second by default
Remarks
—
—
Optional
60 seconds by default