In a system for performing maintenance/management on a subject machine with a maintenance/management control equipment via a network, a connecting section of the machine for the network is implemented in a duplex configuration including a main maintenance/management processing unit and an auxiliary maintenance/management processing unit equipped with respective power supply units independently from each other. When maintenance/management processing is changed over to the auxiliary maintenance/management processing unit from the main unit upon occurrence of fault in the latter, the auxiliary maintenance/management processing unit takes over the network address of the main maintenance/management processing unit for continuing the maintenance/management processing without coming under notice of the maintenance/management control equipment.