Abstract: A communication device redundantly configured with another communication device includes: a first port configured to transmit a packet through a second communication line configuring link aggregation with a first communication line of the other communication device; a second port configured to transmit and receive a packet through a fourth communication line configuring link aggregation with a third communication line of the other communication device; a third port configured to transmit a packet to the other communication device through a fifth communication line; and a first processor configured to: transfer a packet received by the second port to the first port or the third port; detect a failure of the second communication line; detect a failure of the fifth communication line; and shut down the second port when detecting the failure of the second communication line and the failure of the fifth communication line.

Abstract: A communication device redundantly configured with another communication device includes: a first port configured to transmit a packet through a second communication line configuring link aggregation with a first communication line of the other communication device; a second port configured to transmit and receive a packet through a fourth communication line configuring link aggregation with a third communication line of the other communication device; a third port configured to transmit a packet to the other communication device through a fifth communication line; and a first processor configured to: transfer a packet received by the second port to the first port or the third port; detect a failure of the second communication line; detect a failure of the fifth communication line; and shut down the second port when detecting the failure of the second communication line and the failure of the fifth communication line.

Abstract: A transmission device being one of two transmission devices connected with each other among a plurality of transmission devices connected in a ring configuration in a ring protection link, the transmission device includes a processor configured to have a link aggregation connection with a second transmission device not included in the ring configuration, detect a failure with one of the plurality of transmission devices connected in the ring configuration, and when the failure is detected, set a blocking point at a link side port connecting the first transmission device to another one of the plurality of transmission devices connected in the ring configuration.