3Com Switch 7750 Configuration Guide

428 CHAPTER 43: IGMP SNOOPING CONFIGURATION
IGMP Snooping
Implementation
IGMP Snooping terminologies
■ 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.
■ Router port aging timer, multicast member port aging timer, and query
response timer are described in Table 334.
Layer 2 multicast with IGMP Snooping
The switch runs IGMP Snooping to listen to IGMP messages and map the host, the
port corresponding to the host, and the corresponding multicast MAC address.
Figure 107 IGMP Snooping implementation
To implement Layer 2 multicast, the switch processes four different types of IGMP
messages it received, as shown in Table 335.
Table 334 IGMP Snooping timers
Timer Setting
Packet normally
received before
timeout
Timeout action
on the switch
Router port aging
timer
Aging time of the
router port
IGMP general query
message/PIM
message/DVMRP probe
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 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.
IG M P Snooping-enabled Sw itch
IG M P M e s s a g e
Source
IG M P-enabled R outer
IGMP Message