Add new comment
And to be extra clear, it is IGMP Snooping that must be disabled:
IGMP snooping is the process of listening to Internet Group Management Protocol (IGMP) network traffic. The feature allows a network switch to listen in on the IGMP conversation between hosts and routers. By listening to these conversations the switch maintains a map of which links need which IP multicast streams.
Some brands allow a setting PER VLAN.
Cisco may require dedicated/proprietary tool (Cisco Network Assistant) as the built-in web GUI is limited in functionality.