3Com WX1200 3CRWX120695A manual Reenabling Proxy, Reporting, Pseudo-Querier, Changing Igmp Timers

370CHAPTER 18: CONFIGURING AND MANAGING IGMP SNOOPING

Disabling or	Proxy reporting reduces multicast overhead by sending only one report
Reenabling Proxy	for each active group to the multicast routers, instead of sending a
Reporting	separate report from each multicast receiver. For example, if the WX
	switch receives reports from three receivers for multicast group
	237.255.255.255, the switch sends only one report for the group to the
	routers. One report is sufficient to cause the routers to continue sending
	data for the group. Proxy reporting is enabled by default.
	To disable or reenable proxy reporting, use the following command:
	set igmp proxy-report {enable disable} [vlan vlan-id]
Enabling the	The IGMP pseudo-querier enables IGMP snooping to operate in a VLAN
Pseudo-Querier	that does not have a multicast router to send IGMP general queries to
	clients.
	3Com recommends that you use the pseudo-querier only when the VLAN
	contains local multicast traffic sources and no multicast router is servicing
	the subnet.
	To enable the pseudo-querier, use the following command:
	set igmp querier {enable disable} [vlan vlan-id]

Changing IGMP Timers

You can change the following IGMP timers:

„Query interval — Number of seconds that elapse between general queries sent by the WX switch to advertise multicast groups.

„Other-querier-present interval — Number of seconds that the WX switch waits for a general query to arrive from another querier before electing itself the querier.

„Query response interval — Number of tenths of a second that the WX switch waits for a receiver to respond to a group-specific query message before removing the receiver from the receiver list for the group.

The query interval, other-querier-present interval, and query response interval are applicable only when the WX switch is querier for the subnet. For the switch to become the querier, the pseudo-querier feature must be enabled on the switch and the switch must have the lowest IP address among all the devices eligible to become a querier. To enable the pseudo-querier feature, see “Enabling the Pseudo-Querier” on page 370.