If a destination MAC has just aged out, how will the switch forward a received frame for that MAC?

When a switch receives a frame for a destination MAC address that has aged out of its MAC address table, it no longer knows which specific port that MAC address is reachable through. In such a scenario, the switch treats the frame as if it's for an unknown unicast destination. To ensure the frame reaches its intended recipient, the switch floods the frame to all ports within the same VLAN as the ingress port, excluding the ingress port itself. This ensures that if the device is still active, it will receive the frame. The switch does not flood to all VLANs, as that would violate VLAN segmentation. It does not reference an aging table for historical entries or drop the frame, as its primary function is to forward traffic.