3Com Switch 4200G Configuration Guide

250 CHAPTER 29: IGMP SNOOPING CONFIGURATION
IGMP Snooping
Fundamentals
IGMP Snooping terminologies
Before going on, we first describe the following terms involved in IGMP Snooping:
■ Router port: the switch port directly connected to the multicast router.
■ Multicast member port: a switch port connected to a multicast group member (a
host in a multicast group).
■ MAC multicast group: a multicast group identified by a MAC multicast address
and maintained by the switch.
The following three timers are closely associated with IGMP snooping.
Layer 2 multicast with IGMP Snooping
The switch runs IGMP Snooping to listen to IGMP messages and map the hosts and
the ports that connect the hosts to the corresponding multicast group addresses.
Figure 80 IGMP Snooping implementation
Table 220 IGMP Snooping timers
Timer Setting
Message normally
received before
timeout
Timeout action on the
switch
Router port aging
timer
Aging time of the
router port
IGMP general query
message
Consider that this port is
not a router port any more.
Multicast member
port aging timer
Aging time of the
multicast member
ports
IGMP report message Send an IGMP
group-specific query
message to the multicast
member port.
Query response
timer
Query response
timeout time
IGMP report message Remove the port from the
member port list of the
multicast group.
Internet
Internet
IGMP-enabled router
IGMP message
IGMP message
IGMP Snooping-enabled
Ethernet switch