Allied Telesis AT-S79 - Manual (Page 77)

AT-S79 Management Software User’s Guide
Section I: Using the Menus Interface 77
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 network performance.
The AT-GS950 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.