Abstract: According to the present invention, a network device having a plurality of ports, includes a linkup detection unit, a loop detection unit, and a communication shutoff unit. The linkup detection unit detects a linkup of the each port. The loop detection unit detects a loop formed by the network device. The communication shutoff unit shuts off communication on a port on which the linkup was detected at a later time point if the loop is detected.

Abstract: According to the present invention, a network device includes a plurality of ports which are connected to a LAN; a communication controller; and a communication shutoff release unit. The communication controller includes: a linkup detection unit, a loop detection frame sending out unit that sends out the loop detection frame from a linkup detected port, which is a port for which the linkup is detected, after a predetermined period from a time point when the linkup is detected by the linkup detection unit to the local area network, and a loop detection frame detection unit that detects the loop detection frame if the loop detection frame is received on the each port. The communication shutoff release unit releases the shutoff of the communication on the linkup detected port only if the loop detection frame is not detected by the loop detection frame detection unit.

Abstract: According to the present invention, a network device includes a plurality of ports, a communication controller that controls communication on the each port, and a communication shutoff unit that shuts off communication on any of the ports. The communication controller includes a linkup detection unit that detects a linkup of the each port, a loop detection frame sending unit that sends a loop detection frame from a linkup detected port, which is a port for which the linkup is detected after a predetermined period from a time point when the linkup is detected by the linkup detection unit, and a loop detection frame detection unit that detects the loop detection frame if the loop detection frame is received on the each port. The communication shutoff unit shuts off communication carried out on a sending port which is a port from which the detected loop detection frame is sent.

Abstract: According to the present invention, a network device having a plurality of ports, includes a linkup detection unit, a loop detection unit, and a communication shutoff unit. The linkup detection unit detects a linkup of the each port. The loop detection unit detects a loop formed by the network device. The communication shutoff unit shuts off communication on a port on which the linkup was detected at a later time point if the loop is detected.

Abstract: According to the present invention, a network device includes a plurality of ports which are connected to a LAN; a communication controller; and a communication shutoff release unit. The communication controller includes: a linkup detection unit, a loop detection frame sending out unit that sends out the loop detection frame from a linkup detected port, which is a port for which the linkup is detected, after a predetermined period from a time point when the linkup is detected by the linkup detection unit to the local area network, and a loop detection frame detection unit that detects the loop detection frame if the loop detection frame is received on the each port. The communication shutoff release unit releases the shutoff of the communication on the linkup detected port only if the loop detection frame is not detected by the loop detection frame detection unit.

Abstract: According to the present invention, a network device includes a plurality of ports, a communication controller that controls communication on the each port, and a communication shutoff unit that shuts off communication on any of the ports. The communication controller includes a linkup detection unit that detects a linkup of the each port, a loop detection frame sending unit that sends a loop detection frame from a linkup detected port, which is a port for which the linkup is detected after a predetermined period from a time point when the linkup is detected by the linkup detection unit, and a loop detection frame detection unit that detects the loop detection frame if the loop detection frame is received on the each port. The communication shutoff unit shuts off communication carried out on a sending port which is a port from which the detected loop detection frame is sent.