620 Configuring the Spanning Tree Protocolrecognize full-duplex connectivity and ports which are connected to endstations, resulting in rapid transitioning of the port to the Forwarding stateand the suppression of Topology Change Notifications.MSTP is compatible to both RSTP and STP. It behaves appropriately to STPand RSTP bridges. A MSTP bridge can be configured to behave entirely as aRSTP bridge or a STP bridge.How Does STP Work?The switches (bridges) that participate in the spanning tree elect a switch tobe the root bridge for the spanning tree. The root bridge is the switch with thelowest bridge ID, which is computed from the unique identifier of the bridgeand its configurable priority number. When two switches have an equalbridge ID value, the switch with the lowest MAC address is the root bridge.After the root bridge is elected, each switch finds the lowest-cost path to theroot bridge. The port that connects the switch to the lowest-cost path is theroot port on the switch. The switches in the spanning tree also determinewhich ports have the lowest-path cost for each segment. These ports are thedesignated ports. Only the root ports and designated ports are placed in aforwarding state to send and receive traffic. All other ports are put into ablocked state to prevent redundant paths that might cause loops.To determine the root path costs and maintain topology information,switches that participate in the spanning tree use Bridge Protocol Data Units(BPDUs) to exchange information.
