Patent ID: 8064335

Claim:
An external device for use in a communication monitoring system, the communication monitoring system coupling each of a plurality of network apparatuses at a border of a network to such an external device, coupling a predetermined network apparatus of the plurality of network apparatuses to a management system for the network, the external device comprising: a table to store information including representative information about a representative external device coupled to the predetermined network apparatus coupled to the management system, adjacent information about one or more adjacent external devices adjacent to a corresponding network apparatus coupled to the external device, and a status of communication between the representative external device and each of the adjacent external devices; a communication check request transmitter to transmit communication check request information toward the other external devices based on the table; a communication manager to check communication with each of the other external devices using a reply to the communication check request information from the other external devices; a communication break transmitter, in a case where the communication is not confirmed by the communication manager, to transmit communication break notice information toward the management system as a destination when the external device and the representative external device can communicate and to transmit communication break notice information toward one of the adjacent external devices as the destination when the communication between the external device and the representative external device is not confirmed; and a relay, when receiving communication break notice information, to change the destination of the communication break notice information to the management system and to transmit the communication break notice information.