3Com 1100 - Manual (Page 191)

Multicast Filtering and Your Switch 191
Multicast Filtering
and Your Switch Your Switch provides automatic filtering support for two multicast
systems:
■
IEEE 802.1p, which uses the GARP Multicast Registration Protocol
(GMRP)
■
IGMP (Internet Group Management Protocol)
In addition, you can manually configure the filtering and forwarding of
multicasts using Transcend
® Network Management software.
IEEE 802.1p Multicast
Filtering
The IEEE 802.1p standard defines a system that allows network devices to
use a GARP Multicast Registration Protocol (GMRP) to register
endstations with multicast groups. GMRP is protocol-independent, which
means that it can be used on all LANs and VLANs that contain network
devices and endstations which support IEEE 802.1p.
IEEE 802.1p multicast filtering works as follows:
1 If an 802.1p endstation wants to receive traffic for a multicast group, it
sends out a join packet with a known multicast address to declare that it
would like to join that group.
2 When the join packet arrives at a port on a Switch with 802.1p multicast
learning enabled, the Switch specifies that the port is to forward traffic
for the multicast group and then sends a similar packet to all other ports.
3 When traffic for the multicast group appears on the network, the Switch
units only forward the traffic to ports that received a join packet.
Enabling 802.1p Multicast Learning
For information about enabling 802.1p multicast learning for an
individual port on your Switch, see
“Configuring a Port” on page 59 . For
information about enabling 802.1p multicast learning for a whole Switch
or stack, see
“Configuring the Advanced Stack Settings” on page 76 .
For information about configuring IEEE 802.1p functionality on an
endstation, refer to the user documentation supplied with your
endstation or the endstation’s Network Interface Card (NIC).