3Com Router 3031, Command Reference Manual

Page: 705 / 838

IGMP Configuration Commands 705
Parameter
robust-value: IGMP robust coefficient, indicating the times IGMP querier sends the
IGMP specified group query packet when it receives IGMP Leave packet from the
host. The value ranges from 2 to 5. By default, the value is 2.
Description
Using the igmp robust-count command, you can set the times IGMP querier sends
the IGMP specified group query packet when it receives IGMP Leave packet from
the host. Using the undo igmp robust-count command, you can restore the
default value.
On a shared network, with multiple hosts and multicast routers on a network
segment, the query router (querier for short) takes charge of maintaining IGMP
group membership on an interface. When the host in IGMP Version 2 leaves a
group, the host should send IGMP Leave packet. If IGMP querier receives the
packet, it must send the IGMP specified group query packet for robust-value times
according to the interval seconds configured via igmp lastmember-queryinterval
command (if the command is not configured, seconds is 1) and the robust
coefficient robust-value configured via igmp robust-count (if the command is not
configured, robust-value is 2).
If another host receives the IGMP specified group query packet from IGMP querier
and is interested in the group, it will send IGMP Membership Report packet within
the maximum response time regulated by the packet. If IGMP querier receives
IGMP Membership Report packet from another host within the time robust-value x
seconds, it will go on maintaining the group membership. If not, it will regard the
group is overtime and stop maintaining the group membership.
The command is only valid when IGMP query router is running in IGMP Version 2.
If the host runs in IGMP Version 1, it may not send IGMP Leave packet when it
leaves a group. At that time, the command is invalid to the host.
For the related commands, see igmp lastmember-queryinterval and display igmp
interface.
Example
Configure the robust-value of querier on the interface Ethernet1/0/0 to 3.
<3Com-Ethernet1/0/0] igmp robust-count 3
igmp timer
other-querier-present
Syntax
igmp timer other-querier-present seconds
undo igmp timer other-querier-present
View
Interface view
Parameter
seconds: IGMP querier present time, in second. The value ranges from 60 to 300
seconds. By default, the value is twice of IGMP query messages interval. It is 120
seconds in general.