Allied Telesis AT-GS950/48PS - Manual (Page 137)

AT-GS950/48PS Switch Web Interface User’s Guide
137
Without IGMP snooping, a switch floods 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-GS950/48PS switch maintains a list of multicast groups through
an adjustable time out 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.