The port security feature controls the address leaning capability and the traffic forwarding decision. Each port can have this function enabled or disabled. When it is enabled and a number is given said N, which allows N addresses to be learned at this port, the first N learned addresses are locked at this port as a static entry. When the learned address number reaches N, any incoming packet without learned source addresses are discarded (e.g. dropped) and no more new addresses can be learned at this port.