Allied Telesis AT-S81 - Manual (Page 131)

AT-S81 Management Software User’s Guide
Section II: Menus Interface 131
network security by restricting the flow of multicast packets only to those
switch ports connected to host nodes.
Without IGMP snooping a switch would have to flood multicast packets out
all of its ports, except the port on which it received the packet. Such
flooding of packets can negatively impact switch and network
performance.
The AT-8000/8POE Fast Ethernet switch maintains its list of multicast
groups through an adjustable timeout value, which controls how frequently
it expects to see reports from end nodes that want to remain members of
multicast groups, and by processing leave requests.
By default, IGMP snooping is disabled on the switch.