Adding to what's already been mentioned:   If your application is making use of multicast inside an L2 domain (single VLAN) that stretches across multiple switches, and IGMP snooping is enabled on the switches (the default), you will need to be sure that an IGMP querier exists inside the VLAN. If there is no IGMP querier, it can be possible for the multicast streams to be black-holed when they traverse multiple L2 switch hops.   IGMP querier configuration documentation can be found here: https://documentation.meraki.com/zGeneral_Administration/Other_Topics/Multicast_support#IGMP_Querier   For the most optimal forwarding of the multicast streams (avoiding unnecessary forwarding), it will be best to enable the querier on the switch as close to the multicast sources as possible.   NOTE: It is not necessary to enable an IGMP querier on your Meraki switches if another non-Meraki device is connected inside the VLAN that is acting as the querier. If multiple queriers are enabled in a VLAN, only the one with the lowest source IP will be actively querying. ... View more