Multiple instance spanning tree protocol

An intermediate device for use in a computer network having a plurality of virtual local area network (VLAN) designations, the intermediate device comprising:

• a plurality of ports for use in interconnecting the intermediate device to the computer network;
• a spanning tree engine in communicating relationship with the plurality of ports, wherein the spanning tree engine is configured to:
• generate and send from the plurality of ports one or more multiple instance spanning tree protocol bridge protocol data unit (MI-STP BPDU) messages, each MI-STP BPDU containing a spanning tree instance identifier;
• and
• process received MI-STP BPDU message so as to cooperate in establishing a loop-free path for each spanning tree instance identifier;
• and
• a VLAN association engine for mapping, in response to defining a loop-free path for each spanning tree instance identifier, each VLAN designation to a spanning tree instance identifier so that messages tagged with a given VLAN designation may be forwarded along the loop-free path established for the spanning tree instance identifier to which the given VLAN designation is mapped.

A computer readable medium containing executable program instructions for creating multiple spanning trees within a computer network, each spanning tree defining a loop-free path among a plurality of intermediate devices within the network, the network configured with a plurality of virtual local area network (VLAN) designations, the executable program instructions comprising steps for:

• processing received multiple instance spanning tree protocol bridge protocol data unit (MI-STP BPDU) messages, each MI-STP BPDU containing a spanning tree instance identifier, so as to define a loop-free path for each spanning tree instance identifier;
• mapping, in response to defining a loop-free path for each spanning tree instance identifier, each VLAN designation of the computer network to a spanning tree instance identifier;
• and
• distributing messages tagged with a given VLAN designation across the loop-free path for the spanning tree instance identifier to which the given VLAN designation is mapped.

An intermediate device for use in a computer network having a plurality of virtual local area network (VLAN) designations, the intermediate device comprising:

• a plurality of ports for use in interconnecting the intermediate device to the computer network;
• means for generating and sending from the plurality of ports one or more multiple instance spanning tree protocol bridge protocol data unit (MI-STP BPDU) messages, each MI-STP BPDU containing a spanning tree instance identifier;
• means for processing received MI-STP BPDU message so to transition the ports among a plurality of spanning tree port states, including blocking, listening, learning and forwarding states, for each spanning tree instance;
• means for mapping, in response to defining a loop-free path for each spanning tree instance identifier, each VLAN designation to a spanning tree instance identifier;
• and
• means for forwarding messages tagged with a given VLAN designation from ports in the forwarding spanning tree port state for the spanning tree instance to which the given VLAN designation is mapped.