This is the hard ceiling on how many stations (MAC addresses) the switch's address table can hold at once, a fixed hardware/firmware limit rather than a configurable setting. An admin checks this when planning how many end devices a given switch model can support before running into address-table exhaustion and the packet flooding that follows once the limit is reached. For example, an older Catalyst 2600 model might cap out at 4096 stations, which becomes a real constraint in a dense server-farm deployment.