User Manual
Publication date: May, 2005
Revision A1
71
3-7. 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.
Fig. 3-22
Function name:
IGMP Snooping
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.
