3Com Switch 8800 Configuration Guide Chapter 27 IGMP Configuration
27-4
27.2.4 Configuring the Interval to Send IGMP Query Message
Multicast routers send IGMP query messages to discover which multicast groups are
present on attached networks. Multicast routers send query messages periodically to
refresh their knowledge of members present on their networks.
Perform the following configuration in VLAN interface view.
Table 27-3 Configuring the interval to send IGMP query message
Operation Command
Configure the interval to send IGMP query
message igmp timer query seconds
Restore the default value undo igmp timer query
When there are multiple multicast routers on a network segment, the querier is
responsible for sending IGMP query messages to all hosts on the LAN.
By default, the interval is 60 seconds.
27.2.5 Configuring the Interval and the Number of Querying IGMP Packets
On the shared network, it is the query router (querier) that maintains IGMP membership
on the interface. The following commands are used to configure the interval and times
of sending IGMP group-specific query packets for the querier when it receives an IGMP
leave message from a host.
z The host sends the IGMP Leave message.
z Upon receiving the message, IGMP querier sends the group-specific IGMP query
message for specified times (defined by the robust-value in igmp robust-count,
with the default value as 2) and at a time interval (defined by the seconds in igmp
lastmember-queryinterval, with the default value as 1 second).
z When other hosts reciver the message from the IGMP querier and are interested
in this group, they return the IGMP Memberhsip Report message within the
defined maximum response time.
z If IGMP querier receives the report messges from other hosts within the period
equal to robust-value × seconds, it continues memberhship maintenance for this
group.
z If it receives no report message from any other host within this peroid, it reckens
this as timeout and ends mebership 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 IGMP Leave Group message when it leaves a
group.
Please perform the following configurations in VLAN interface view.