This read-only Counter counts how many times the switch's overall address table was completely full when trying to add an entry learned on this port, as opposed to just one hash chain being full. This is a more severe symptom than a single chain overflow, since it means the switch-wide table capacity itself has been exhausted, not just an unevenly distributed hash bucket. Seeing this counter increment on multiple ports simultaneously indicates the whole switch, not just one busy port, has outgrown its address table.