Patent ID: 8724478

Claim:
A network device to be used as a replacement for a monitoring device as an object to be replaced, the monitoring device being provided as part of a ring network and configured to monitor status of the ring network by repeatedly sending a control frame used to monitor the status of the ring network from one of two ring ports and receiving the control frame at the other of the two ring ports, the network device comprising: a link-up detector configured to detect that two ring ports of the network device are set in link-up state, when the network device is connected between first and second adjacent network devices, which are located adjacent to the monitoring device in the ring network, to be arranged in parallel with the monitoring device; a forwarding instructor configured to, when the link-up state is detected by the link-up detector, give an instruction to forward the control frame by a forwarding route going through the network device, to the first adjacent network device connected with the ring port of the monitoring device that receives the control frame, out of the first and second adjacent network devices; and a replacement-time monitor configured to monitor the status of the ring network by receiving the control frame sent from the first adjacent network device.