Command Reference Guide

3Com Router 3000 Ethernet Family
Command Reference Guide Chapter 2 IGMP Configuration Commands
3Com Corporation
2-10
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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
Use the igmp robust-count command to set the times IGMP querier sends the IGMP
specified group query packet when it receives IGMP Leave packet from the host.
Use the undo igmp robust-count command to restore the default value.
On a shared network, that is, when there are 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.
Related command: 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
2.1.13 igmp timer other-querier-present
Syntax
igmp timer other-querier-present seconds
undo igmp timer other-querier-present