Patent ID: 7480258

Claim:
In a plurality of intermediate network devices having a plurality of ports for forwarding network messages within a bridged network having a root, the plurality of intermediate network devices organized as a stack, each intermediate network device having a stack port for use in communicating with the other network devices of the stack, a method for efficiently transitioning the ports among a plurality of spanning tree protocol (STP) states, the method comprising the steps of: executing the STP at each intermediate network device of the stack so as to assign the stack port of each device to either a Root Port Role or a Designated Port Role, and to assign a non-stack port at a single device of the stack to the Root Port Role; transitioning the ports assigned to the Root Port Role and the Designated Port Role to a forwarding STP state; designating all non-stack ports at the devices of the stack that provide connectivity to the root, other than the non-stack port assigned to the Root Port Role, as Alternate Stack Root Ports; transitioning the Alternate Stack Root Ports to a discarding STP state; and in response to a failure at the non-stack port assigned to the Root Port Role, transitioning a selected one of the Alternate Stack Root Ports from the discarding STP state directly to the forwarding STP state, without transitioning the selected port through any intermediary STP states, so that the selected Alternate Stack Root Port assumes Root Port Role for the stack.