Allied Telesis AT-S101 - Manual (Page 115)

AT-S101 Management Software User’s Guide
115
Without IGMP snooping, a switch would have to flood multicast packets
from all of its ports, except the port on which it received the packet. Such
flooding of packets can negatively impact network performance.
The AT-GS950/8POE switches maintain a 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.
Note
By default, IGMP snooping is disabled on the switch.