3Com Switch 8800 Configuration Guide Chapter 27 IGMP Configuration27-2address is elected as the querier when there are multiple multicast routers on the samenetwork segment.II. Leaving group mechanismIn IGMP Version 1, hosts leave the multicast group quietly without informing themulticast router. In this case, the multicast router can only depend on the timeout of theresponse time of the multicast group to confirm that hosts leave the group. In Version 2,when a host is intended to leave, it will send a leave group message if it is the host whoresponds to the latest membership query message.III. Specific group queryIn IGMP Version 1, a query of a multicast router is targeted at all the multicast groupson the network segment, which is known as General Query.In IGMP Version 2, Group-Specific Query is added besides general query. Thedestination IP address of the query packet is the IP address of the multicast group. Thegroup address domain in the packet is also the IP address of the multicast group. Thisprevents the hosts of members of other multicast groups from sending responsemessages.IV. Max response timeThe Max Response Time is added in IGMP Version 2. It is used to dynamically adjustthe allowed maximum time for a host to respond to the group query message.27.2 IGMP ConfigurationAfter the multicast function is enabled, you must enable IGMP on the interface first andthen perform other IGMP configurations.1) IGMP basic configuration includes:z Enabling multicastz Enabling IGMP on an interface2) IGMP advanced configuration includes:z Configuring a router to join specified multicast groupz Controlling the access to IP multicast groupsz Configuring the IGMP query message intervalz Configuring the IGMP versionz Configuring the IGMP querier present timerz Configuring the maximum query response timez Configuring the times of sending IGMP Group-Specific Query packetz Configuring the interval of sending IGMP Group-Specific Query packetz Configuring the limit of IGMP groups on an interfacez Deleting IGMP Groups Joined on an Interface
