PURPOSE: To switch over a communication processor to a stand-by communication processor easily, speedily, and efficiently.

CONSTITUTION: A communication processor state monitor means 1 monitors whether or not a fault has occurred in a communication processor 63, and when a communication processor switching judging means judges that the fault matches a communication processor switching event registered previously in a network state registration table, a network resource information loading means 3 loads network definition information to the stand-by communication processor 64 and further a system activating means 4 activates a device group related with the stand-by communication processor 65. After the communication processor is switched over, the communication processor state monitor means 1 monitors the restoration of the communication processor 63 and after the communication processor is restored, a table altering means 5 registers the communication processor as the stand-by communication processor.