Abstract: When a first switching device receives a control frame such as IGMP report at a MLAG port, it learns a multicast (MC) group contained in the control frame in association with the MLAG port on a MC address table. Also, the first switching device generates a bridge control frame containing the control frame and an identifier of the MLAG port and transfers it from a bridge port. On the other hand, when the second switching device receives the bridge control frame at the bridge port, it detects the control frame and the identifier of the MLAG port from the bridge control frame and learns the MC group contained in the control frame in association with its own MLAG port on the MC address table.

Abstract: In a multi-chassis link-aggregation device, each of first and second switch devices is provided with a relay condition, which defines prohibition of a predetermined relay path. If there is no link failure in each multi-chassis link-aggregation device, each of the first and second switch devices prohibits forwarding of a frame, which has been received by a bridge port, from each multi-chassis link-aggregation device. On the other hand, if a link failure is present in a second port (second multi-chassis link-aggregation device) of the first and second switch devices permits forwarding of the frame, which has been received by the bridge port, from the second port. In this case, if a destination port of the frame received by a first port includes the second multi-chassis link-aggregation device, the first switch device adds a port identifier representing the received port to the frame and forwards that toward the second switch device.

Abstract: An address table can be easily shared (synchronized) between two switching devices for which multi-chassis link aggregation is set. When a destination port of a frame received at a port P2 is a port P1, one of the two switching devices for which the multi-chassis link aggregation is set creates a bridging frame containing a transmission source address contained in the flame and an identifier of the port which has received, and transfers the bridging frame from a bridging port. When the other of the two switching devices receives the bridging frame, the other of the two switching devices detects the identifier of the port which has received and the transmission source address from the frame, and updates an address table of its own based on the identifier, the transmission source address, and a link table of its own.

Abstract: In order to provide a communication system and a communication system processing method with which fault resistance is improved and also signal loopback can be prevented, a communication system is provided with, for example, port switches SWP1 to SWP3, fabric switches SWF1 and SWF2, and user switches SWU1 and SWU2, and SWP1 and SWP2 are connected by a common communication line between redundancy ports Pr to thereby form the same domain group (MLAG) and logically function as one switch. Each of SWF1 and SWF2 sets, for ports P1 and P2 to which SWP1 and SWP2 that are constituent elements of the same domain group are connected, a sublink SLK that causes the ports P1 and P2 to logically function as one port.

Abstract: A communication system includes a redundancy network, which includes first and second switch apparatuses and employs a ring protocol or the like, and third switch apparatuses. The first and second switch apparatuses function logically as a signal switch apparatus (MLAG). Each third switch apparatus operates with link aggregation (LAG) being set between the third switch apparatus and the first and second switch apparatuses. When a failure occurs in communication between redundant ports of the first and second switch apparatuses, a fourth switch apparatus supporting the ring protocol performs control to put master and slave ports thereof into an open state and the second switch apparatus performs control to put user ports thereof into a blocking state.