3Com Switch 7750 Configuration Guide Guide

Overview 387
Figure 92 IGMP Snooping implementation
To implement Layer 2 multicast, the switch processes four different types of IGMP
messages it received, as shown in
Table 305.
Table 305 IGMP Snooping messages
Message Sender Receiver Purpose Action of the multicast member switch
IGMP
general
query
message
Multicast
router
and
multicast
switch
Multicast
member
switch
and host
Query if
the
multicast
groups
contain
any
member
Check if the message
comes from the original
router port
If yes, reset the aging
timer of the router port
If not, notify the
multicast router that a
member is in a
multicast group and
start the aging timer for
the router port
IGMP
group-sp
ecific
query
message
Multicast
router
and
multicast
switch
Multicast
member
switch
and host
Query if a
specific
IGMP
multicast
group
contains
any
member
Send an IGMP group-specific query message to
the IP multicast group being queried.
Internet
Internet
IGMP-enabled router
IGMP message
IGMP message
IGMP Snooping-enabled
Ethernet switch