Abstract: A network system which facilitates the task of replacing switches pertaining to a detected link failure. A server network is formed from a plurality of switches and links. The link state of each port on the switches is being monitored by a link-down detector, and a switch port that has entered a link-down state from a link-up state is identified as an inoperative port. Upon detection of such a link-down event, a function disabler disables link functions of specified ports of other switches in the switch group to which the switch having the inoperative port belongs, so that the servers on the network will change their setups all at once and continue the communication through new paths.