Abstract: A cross stack rapid transition protocol is provided for permitting multiple network devices organized as a stack to rapidly transition their ports in response to network changes so as to minimize traffic flow disruptions while avoiding loops. Each switch in the stack has a stack port that connects the switch to another switch in the stack, and a plurality of ports for connecting the switch to other entities of the computer network. Each switch includes a Spanning Tree Protocol (STP) entity that transitions the ports of the switch among a plurality of states including a forwarding state and a blocking state. Each switch also tracks which other switches are members of the switch stack. The stack port of each switch is transitioned to the forwarding state, and a single switch having connectivity to a root is elected to be a Stack Root. One or more other switches may have Alternate Stack Root Ports, that provide alternate paths to the root.