3Com Switch 7750 Configuration Guide

430 CHAPTER 43: IGMP SNOOPING CONFIGURATION
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CAUTION: An IGMP-Snooping-enabled Switch 7750 Ethernet switch judges
whether the multicast group exists when it receives an IGMP leave packet sent by
a host in a multicast group. If this multicast group does not exist, the switch will
drop the IGMP leave packet instead of forwarding it.
IGMP Snooping
Configuration
IGMP
leave
message
Host Multicast
router
and
multicast
switch
Notify
the
multicast
router
and
multicast
switch
that the
host is
leaving
its
multicast
group.
Multicast router and multicast
switch send IGMP specific
group query message(s) to the
multicast group whose member
host sends leave messages to
check if the multicast group has
any members and enable the
corresponding query timer.
If the multicast
group responds,
the switch
checks whether
the port is the
last host port
corresponding
to the MAC
multicast group.
■ If yes,
remove the
correspondi
ng MAC
multicast
group and IP
multicast
group
■ If no,
remove only
those entries
that
correspond
to this port
in the MAC
multicast
group, and
remove the
correspondi
ng IP
multicast
group
entries
If no response is
received from
the multicast
group before
the timer times
out, notify the
router to
remove this
multicast group
node from the
multicast tree
Table 335 IGMP Snooping messages
Message Sender Receiver Purpose Action of the multicast member switch
Table 336 IGMP Snooping configuration tasks
Operation Description Related section
Enable IGMP Snooping Required “Enabling IGMP Snooping” on page 431
Configure IGMP Snooping
version
Optional “Configuring the Version of IGMP
Snooping” on page 431