A network switch includes: a table record portion that records an address solution table that records multiple address information; an information addition portion that adds new address information for a new communication device based on the address solution data to the address information table; a relay portion that relays data other than the address solution data; and a rewrite portion that rewrites at least one of the address solution table or propriety information in accordance with an external instruction output from an external device. The address solution table includes the propriety information indicating availability propriety of the address information for each of the multiple address information. The relay portion relays the data by utilizing the address information set to be utilizable in the propriety information.