Allied Telesis AT-S62 - Manual (Page 205)

AT-S62 User’s Guide
Section II: Advanced Operations 205
Without IGMP snooping a switch would be obligated 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-8524M 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.
Note
By default, IGMP snooping is disabled on the switch.