1. An address learning method for a network device having a plurality of connection ports, at least one of which is electrically connected to a terminal device, the method comprising: a fetching process for fetching an address data string from a first memory unit by a programmable logic device; a hashed-address generating process for generating a hashed-address by the programmable logic device; a data registering process for writing the address data string into a data table; and an address registering process for writing the hashed-address into a hashed-address table.