Abstract: Ports of a switch are assigned by a person, for example a network manager, to be for communication up the spanning tree toward the root switch (“up ports”), or down the spanning tree away from the root switch (“down ports”). This assignment is made by enabling “Uplinkguard” status for a desired up port, and by connecting the desired port to a switch which it is desired to place in the higher layer of the spanning tree. A port having Uplinkguard enabled is prevented, for example by software or firmware in its switch, from transitioning to a designated role. Uplinkguard-enabling a port, by preventing the port from transitioning to the designated role, has at least two consequences: preventing the port from being selected by the STP to transmit to lower switches in the spanning tree; and, preventing the port from transmitting when a one way connectivity fault develops on that port. A port with Uplinkguard enabled may transition to root port role.

Abstract: A method and apparatus allows for continued operation of one or more applications running at a network device with reduced delay despite crashes or failures at that device. The network device includes two or more supervisor cards for running the applications and a plurality of line cards. According to the invention, one supervisor card is designated the active supervisor card and one supervisor card is designated the standby supervisor card. As changes in state and other operating conditions take place on the active supervisor events are generating for passing at least some of this information to the standby supervisor where it is stored. Following a crash or failure of the active supervisor card, the standby becomes the newly active supervisor card. The standby supervisor performs a consistency check with the line cards and resets those that fail the check.

Abstract: The Spanning Tree Protocol (STP) chooses a root switch. Each of the other switches has a “root” port and one or more “designated ports(s)” chosen by STP. Packets are transmitted upstream toward the root switch through the root port, and packets designated for downstream switches from the root switch are received by the root port and transmitted through the designated ports. In the invention, an administrator of the core network identifies which switch ports in the core network are boundary ports to customer networks. The administrator designates the boundary ports as “root guard protected” ports (RG ports). The STP then executes as required by the ordinary STP protocol, and if a RG port is selected by the STP to be a root portm then the status of the port is set to “blocked,” and no packets are transmitted through the port.

Abstract: A multiple instance spanning tree protocol (MI-STP) creates a plurality of active topologies (i.e., loop-free paths) within a computer network. These active topologies may be established through the exchange and processing of multiple instance spanning tree bridge protocol data unit messages (MI-STP BPDUs) by the intermediate network devices within the network. The active topologies are preferably created independently of any virtual local area network (VLAN) designations defined within the network. Once the active topologies are defined, each VLAN designation is then mapped to a single active topology, although multiple VLAN designations are preferably mapped to the same active topology to provide load balancing.

Abstract: A method and apparatus for continuing the operation of a spanning tree protocol at a network device despite crashes or failures at that device. A supervisor card contained in the network device is designated an active supervisor, while all other supervisor cards are designated standby supervisors. The active supervisor runs the spanning tree protocol, and informs the standby supervisors of the states of ports, but not of the identity of the root or designated bridges. When a crash or failure occurs at the active supervisor, one of the standby supervisors is immediately designated to be the new active supervisor. The newly active supervisor reviews the port state, and queries the line cards to determine whether that port state information is still valid. The newly active supervisor adopts the valid port state information, leaving those ports in their current spanning tree port state.

Abstract: Ports of a switch are assigned by a person, for example a network manager, to be for communication up the spanning tree toward the root switch (“up ports”), or down the spanning tree away from the root switch (“down ports”). This assignment is made by enabling “Uplinkguard” status for a desired up port, and by connecting the desired port to a switch which it is desired to place in the higher layer of the spanning tree. A port having Uplinkguard enabled is prevented, for example by software or firmware in its switch, from transitioning to a designated role. Uplinkguard enabling a port, by preventing the port from transitioning to the designated role, has at least two consequences: preventing the port from being selected by the STP to transmit to lower switches in the spanning tree; and, preventing the port from transmitting when a one way connectivity fault develops on that port. A port with Uplinkguard enabled may transition to root port role.

Abstract: An apparatus and method for preventing the disruption of Fibre Channel Fabrics caused by ReConfigure Fabric (RCF) messages is disclosed. The apparatus includes a storage area network and a plurality of Fibre Channel Switches arranged in a Fabric. Each of the plurality of Switches includes logic to selectively configure their Ports to either reject or accept RCF messages. When configured to reject RCF messages, the Switch Port that receives an RCF message will generate a reject message along with a reason code explanation “E_Port Isolated”, and then transition into an Isolated state. When the Switch that generated the RCF message receives the reject message, its Port also transition into the Isolated state. In accordance with the method of the present invention, either a Storage Service Provider or a client can access the Switches of the Fabric through either a command line interpreter or a management application.

Abstract: High availability for a fibre channel switch in a storage area network can be implemented using redundant supervisors. An active supervisor can identify high availability characteristics associated with a message and determine whether the message should be mirrored onto a redundant supervisor, logged, and/or made persistent. Messages can be logged in a pending transaction buffer and stored using persistent storage services. Mirroring can be performed using synchronization queues that allow messages to be passed asynchronously to a redundant supervisor while maintaining full synchronization between supervisors and causing little delay to operation of the active supervisor.