The port security feature controls the address learning 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 addresses number reaches N, any incoming packet that has not learned a source address is discarded (e.g. dropped) and no more new addresses can be learned on this port.