Authentication switch and network system

An authentication switch monitors a failure of an external server, and redirect information to a Web server that holds authentication information registration screen data is provided to a terminal using a monitoring result. A life-and-death monitoring control unit for monitoring life and death of an external Web server is disposed within an authentication switch to monitor the life and death of the external Web server. An authentication processing unit within the authentication switch switches the redirect information on the basis of a life-and-death monitoring table of the external Web server provided in the life-and-death monitoring control unit in response to an authentication request from the terminal, and enables web authentication even when the external Web server is in failure.