If a Nexus switch receives a frame and no MAC table entry is found for the destination, what will take place?

Dropping unknown-destination frames is not standard Layer 2 switch behavior; frames are only dropped due to errors, security policies, or explicit ACL denials, not because the destination MAC is unknown.

Flooding is the standard Layer 2 behavior for unknown unicast frames because the switch has no information about which port leads to the destination. This flood-and-learn process ensures the frame reaches its destination while also allowing the switch to learn the destination's MAC address when that device sends a return frame.

Ethernet switching at Layer 2 is connectionless and has no mechanism to notify the sender that a destination MAC address was not found; that type of feedback does not exist in standard switch operation.

MAC address learning records the source address of a received frame against its ingress port - not the destination address - so an unknown destination address cannot be learned from the incoming frame itself.