3Com 5500-SI Configuration Manual page 329

Configuring the Interval for Querying IGMP Packets
The router finds out which multicast groups on its connected network segment have
members by sending IGMP query messages periodically. Upon the reception of a
response message, the router refreshes the membership information of the
corresponding multicast group.
Perform the following configurations in Interface View.l
Table 330 Configuring query interval
Operation
Configure query interval
Restore the default query interval
When there are multiple multicast routers on a network segment, the querier is
responsible for sending IGMP query messages to all the hosts on the LAN.
By default, the interval is 60 seconds.
Configuring the Interval and the Number of IGMP Query Packets
On a shared network, the query router (querier) maintains IGMP membership on the
interface. When an IGMP querier receives an IGMP Leave Group message from a host,
the last member query interval can be specified for Group-Specific Queries.
1 The host sends the IGMP Leave message.
2 Upon receiving the message, the IGMP querier sends the designated group IGMP
query message for the specified number of times (defined by the
igmp robust-count
(defined by the
seconds
value as 2).
3 When other hosts receive the message from the IGMP querier and are interested in
this group, they return the IGMP Membership Report message within the defined
maximum response time.
4 If the IGMP querier receives the report messges from other hosts within the period
equal to robust-value × seconds, it continues membership maintenance for this
group.
5 If the IGMP querier does not receive a report message from any other host within this
period, then it takes it as timeout and ends membership maintenance for this group.
This command can be used only when the querier runs IGMP version 2, since a host
running IGMP Version 1 does not send an IGMP Leave Group message when it leaves
a group.
Perform the following configuration in Interface View.
Configure interval for querying IGMP packets, see Table 331. By default, the
■
interval is 1 second.
Configuring the number of last member querying, see Table 332. By default, an
■
IGMP group-specific query message is sent for twice
Internet Group Management Protocol (IGMP) 329
Command
igmp timer query seconds
undo igmp timer query
, with the default value as 1 second) and at a time interval
in
igmp lastmember-queryinterval
in
robust_value
, with the default