Patent ID: 7792016

Claim:
A network relay device that has a direct link and multiple ports, and works to relay data in a network, in combination with at least one specific network device among multiple network devices linked to the multiple ports via multiple lines, the network relay device comprising: a control module that receives and sends control messages from and to the specific network device via the direct link and switches over an operating status of the network relay device between master and backup; and a communication module that is under control of the control module and, in the master operating status of the network relay device, sets a connection status of the multiple lines connected with the multiple ports to logic connection to enable transmission of both messages and the data, while in the backup operating status of the network relay device, setting the connection status of the multiple lines connected with the multiple ports to logic disconnection to enable only transmission of messages but disable transmission of the data, in the case of detection of failure on the direct link in the backup operating status of the network relay device, the control module verifying reception of a partial failure message representing occurrence of partial failure in the specific network device from the specific network device via any of the multiple lines linked to the multiple ports and identifying partial failure occurring in the specific network device, wherein upon identification of the partial failure occurring in the specific network device, the control module sends a switchover message to the specific network device to urge a switchover of an operating status of the specific network device from master to backup via a line connected to a port receiving the partial failure message, receives a return message from the specific network device, and switches over the operating status of the network relay device from backup to master.