3Com Switch 8800 Advanced Software V5 Configuration Guide

Configuring IGMP Performance Parameters 531
case, IGMP messages are directly passed to the upper layer protocol, no matter
whether the IGMP messages carry the Router-Alert option or not.
To enhance the device performance and avoid unnecessary costs, and also for the
consideration of protocol security, you can configure the device to discard IGMP
messages that do not carry the Router-Alert option.
Configuring IGMP packet options globally
Follow these steps to configure IGMP packet options globally:
Configuring IGMP packet options for an interface
Follow these steps to configure IGMP packet options for an interface:
Configuring IGMP
Timers
The IGMP querier periodically sends IGMP general queries to decide whether any
multicast group member exists on the network. The network administrator can
tune the IGMP general query interval based on actual condition of the network.
Upon receiving an IGMP query (general query or group-specific query), a host
starts a delay timer for each multicast group it has joined. This timer is initialized to
a random value in the range of 0 to the maximum response time, which is derived
from the Max Response Time field in the IGMP query. When the timer value comes
down to 0, the host sends an IGMP report to the corresponding multicast group.
An appropriate setting of the maximum response time for IGMP queries allows
hosts to respond to queries quickly and avoids bursts of IGMP traffic on the
network caused by reports simultaneously sent by a large number of hosts when
the corresponding timers expires simultaneously.
To do... Use the command... Description
Enter system view system-view -
Enter IGMP view igmp -
Configure the router to
discard any IGMP message
that does not carry the
Router-Alert option
require-router-alert Optional
By default, the device does
not check the Router-Alert
Enable the insertion of the
Router-Alert option into IGMP
messages
send-router-alert Optional
By default, IGMP messages
carry the Router-Alert option
To do... Use the command... Description
Enter system view system-view -
Enter VLAN/POS interface
view
interface interface-type
interface-number
-
Configure the interface to
discard any IGMP message
that does not carry the
Router-Alert option
igmp require-router-alert Optional
By default, the device does
not check the Router-Alert
Enable the insertion of the
Router-Alert option into IGMP
messages
igmp send-router-alert Optional
By default, IGMP messages
carry the Router-Alert option