KTI Networks KS-2262 User Manual

Page 72

3-6. IGMP Snooping

The function, IGMP Snooping, 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.

Fig. 3-18

Function name:

IGMP Snooping Status

Function description:

IGMP is used to snoop the status of IP multicast groups and display its
associated information in both tagged VLAN and non-tagged VLAN networks.
Enabling IGMP with either passive or active mode, you can monitor the IGMP
snooping information, which contains the multicast member list with the
multicast groups, VID and member port.