When zyMulticastUnknownMulticastFrameForwarding is drop or drop-vlan and the switch receives an unknown multicast frame, the action will work on the switch. Unknown multicast frames are addressed to multicast groups for which the Switch has not recorded any group members. Select drop(1) to not forward the frame(s). Select forwarding(2) to forward the frame(s) to querier port(s) of the same domain. Select forwarding-vlan(3) to forward the frame(s) to querier port(s) on the specific VLAN(s).