Dell M6220 User Configuration Manual page 711

GMRP is similar to IGMP snooping in its purpose, but IGMP snooping is
more widely used. GMRP must be running on both the host and the switch to
function properly and IGMP/MLD snooping must be disabled on the switch,
as IGMP snooping and GMRP cannot simultaneously operate within the
same VLAN.
711
Configuring L2 Multicast Features