In a computer system having a storage device, switches and hosts respectively connected by a network, in accordance with an ID of a logical volume of the storage device and an IP address of a host, access control configuration of the logical volume is performed relative to the storage device, the IP address of the host is converted into a MAC address, the MAC address of the host is converted into a port ID of the switch connected to the host, and addition of the port to virtual local area network (VLAN) is performed for the switch. Logical unit number (LUN) masking and VLAN configuration essential for security countermeasure of IP-SAN (Internet protocol-storage area network) can be managed collectively by a system administrator so that the running cost of IP-SAN can be lowered.