Unknown unicast packet flooding (UUFB) limits unknown unicast flooding in the forwarding path to prevent the security risk of unwanted traffic reaching the VMs. UUFB prevents packets received on both vEthernet and Ethernet interfaces destined to unknown unicast addresses from flooding the VLAN. When UUFB is applied, VEMs drop unknown unicast packets coming in on the uplink ports.
After you disable unknown unicast packets globally, you can then allow unicast flooding on either a single interface or all interfaces in a port profile.
You can also configure an interface or a port profile to never allow unknown unicasts to be blocked.