User`s manual

185
3-15. Multicast
The function, Multicast, is used to establish the multicast groups to forward
the multicast packet to the member ports, and, in nature, avoids wasting the
bandwidth while IP multicast packets are running over the network. This is because
a switch that does not support IGMP or IGMP Snooping can not tell the multicast
packet from the broadcast packet, so it can only treat them all as the broadcast
packet. Without IGMP Snooping, the multicast packet forwarding function is plain
and nothing is different from broadcast packet.
A switch supported IGMP Snooping with the functions of query, report and
leave, a type of packet exchanged between IP Multicast Router/Switch and IP
Multicast Host, can update the information of the Multicast table when a member
(port) joins or leaves an IP Multicast Destination Address. With this function, once a
switch receives an IP multicast packet, it will forward the packet to the members
who joined in a specified IP multicast group before.
The packets will be discarded by the IGMP Snooping if the user transmits
multicast packets to the multicast group that had not been built up in advance.
3-15-1 IGMP Mode
Function name:
IGMP Mode
Function description:
IGMP mode to select the switch to issue IGMP host messages on behalf of
hosts that the system discovered through standard IGMP interfaces. The
switch acts as a proxy or snooping for its hosts.
Fig. 3-160 IGMP Proxy
Parameter description:
Disable:
To disable the IGMP service on the switch.
Proxy :
To select and enable the IGMP mode with a proxy on the switch.
Snooping:
To select and enable the IGMP mode with a snooping on the switch.