This read-only Counter counts how many times, specifically for this port, an address hash chain was already full when the switch tried to add a new learned station to this port's table. This is the per-port version of the switch-wide ciscoTsStackSwitchAddressTblFulls, letting an admin identify which specific port is driving address-table pressure rather than just knowing the switch overall is struggling. A port showing a disproportionately high count here, relative to its peers, points at that port serving an unusually large or high-churn population of stations.