Networking / AV-IT
IGMP Snooping
01 — Definition
The switch feature that listens to IGMP messages to learn which ports have devices subscribed to a given multicast group. Without it, multicast traffic (sACN, NDI multicast) floods every port exactly like broadcast; with it, the traffic goes only to the ports that actually subscribed.
02 — In the field
Symptom of missing IGMP snooping on a large sACN rig: devices with nothing to do with lighting climb in CPU usage or start dropping packets, because the sACN multicast is flooding everything. Enable IGMP snooping — it is on by default on any good managed switch, but verify anyway.
04 — Sources
- RFC 4541 §2.1 — sans snooping, le trafic multicast est relayé sur toutes les interfaces