User Manual

Moxa’s Managed Switch Next Generation OS (v3.x) User Manual
89
Multicast
Multicast filtering improves the performance of networks that carry multicast traffic. This section will explain
the Layer 2 multicast settings, such as IGMP Snooping, GMRP, and Static Multicast.
IGMP Snooping
IGMP Snooping Overview
IGMP stands for Internet Group Management Protocol, which is a network communication protocol that
hosts nearby routers on networks to construct multicast group memberships.
IGMP snooping allows a network switch to listen in on the IGMP conversation between hosts and routers. By
listening to these conversations, the switch maintains an association mapping table between port(s) and
multicast group.
How IGMP Snooping Works
A switch will, by default, flood multicast traffic to all the other ports, aside ingress, in a broadcast domain
(or the VLAN equivalent). Multicast can cause unnecessary loading for host devices by requiring them to
process packets they have not solicited. IGMP snooping is designed to prevent hosts on a local network from
receiving traffic for a multicast group they have not explicitly joined. It provides switches with a mechanism
to forward multicast traffic to specific ports that receive IGMP hosts. Hence, IGMP snooping can utilize the
network bandwidth more efficiently.
Without IGMP Snooping