Provided is a computer system capable of cutting the cost of running and managing a company network and improving the security of the network by reducing wrong settings and skipped settings due to human factor. The computer system has switches which constitute a network, a management computer which is connected to the network and manages the network, and clients which are connected to the switches. The management computer sets each switch such that client authentication is executed at port provided in the switch that can be connected to the client. The client authentication is processing of verifying whether the client has the right to connect to the network.