3Com 5500-EI PWR Install Manual page 363

If the IGMP querier receives IGMP report messages from other hosts within the period of
robust-value x lastmember-queryinterval, it will maintain the membership of the group.
If the IGMP querier does not receive IGMP report messages from other hosts after the period of
robust-value x lastmember-queryinterval, it considers that the group has no members on the local
subnet and removes the forwarding table entry for the group.
You can use the igmp max-response-time command to set the maximum response time for general
IGMP query messages, while that of an IGMP group-specific query message is determined by
robust-value x lastmember-queryinterval.
The procedure is only fit for the occasion where IGMP queriers run IGMP version 2.
IGMP querier election
On a subnet containing multiple IGMP-enabled interfaces, the one with the lowest IP address becomes
the IGMP querier. If non-querier interfaces receive no query message within the period configured in the
igmp timer other-querier-present command, the current IGMP querier is considered to be down. In
this case, a new IGMP querier election process takes place.
The maximum response time of IGMP general query messages
When the host receives a general query message, it will set a timer for each of its multicast groups. The
timer value is selected from 0 to the maximum response time at random. When the value of a timer
decreases to 0, the host will send the membership information of the multicast group.
By configuring reasonable maximum response time, you can enable the host to respond to the query
information quickly and enable the Layer 3 switch to understand the membership information of
multicast groups quickly.
Follow these steps to configure options related to IGMP query messages:
To do...
Enter system view
Enter interface view
Configure the query interval
(interval of sending general
queries)
Configure the interval of
sending IGMP group-specific
query messages
Configure the number of times
of sending IGMP group-specific
query messages
Configure the other querier
present timer
Use the command...
system-view
interface interface-type
interface-number
igmp timer query seconds
igmp
lastmember-queryinterval
seconds
igmp robust-count
robust-value
igmp timer
other-querier-present
seconds
8
Remarks
—
—
Optional
60 seconds by default.
Optional
1 second by default
Optional
2 by default.
Optional
The system default is 120
seconds, namely twice the
query interval.