Communication relay device with redundancy function for line in network in accordance with WAN environment and communication system using the same

摘要

A communication relay device with a redundancy function for a line in a network under a WAN environment is connected to another, having a one-to-one relationship at both ends of each line by first and second ports to configure a redundancy channel between lines. A closed port setting section sets one of the ports as a closed port, thereby configuring a network free of a loop between the respective lines. A closed port setting information notifying section notifies a counterpart communication relay device connected to the one port, via the one port, of closed port setting notifying information for notifying that one of the ports has been set as a closed port. A datagram transmission stopping section stops transmission of a datagram from a port of its own connected to the one port set as the closed port when receiving the closed port setting notification information as the counterpart communication relay device.