Networking / AV-IT
IGMP Querier
01 — Definition
The link that keeps IGMP snooping standing up: one device per VLAN has to take on the querier role and periodically ask hosts which multicast groups they still want. With no active querier, switches age out their multicast membership tables and either flood the multicast or, worse, drop it — sACN or NDI multicast that worked at power-on stops after a couple of minutes.
02 — In the field
Multicast (sACN, NDI, AES67) works right after boot then dies after 1 to 3 minutes? There is no querier on the VLAN. Enable an IGMP querier on the core switch or the router for that subnet.
04 — Sources
- RFC 3376 §8.2 — Query Interval par défaut 125 s ; §8.4 Group Membership Interval