User’s Guide
Introduction to Spanning Tree Protocol Parameters
The Spanning Tree Protocol works on two levels: the bridge (i.e., switch) and port levels. At the bridge level, the STP algorithm calculates a bridge identifier for each bridge and then determines the root bridge and the designated bridges. On the port level, the spanning tree protocol determines the root port and designated ports.
On the bridge level, these terms are used:
♦Root Bridge The bridge with the
♦Designated Bridge A bridge becomes the designated bridge for a network segment if it has a lower root path cost to the root bridge than the other bridges on the same segment. If all bridges have the same root path cost, then the one with the lowest bridge identifier becomes the designated bridge. Since the root path cost of the root bridge is zero, the root bridge automatically becomes the designated bridge for the segments connected onto it.
♦Bridge Identifier This is a combination of the bridge priority (a parameter you can set) and the bridge MAC address (a unique, unchangeable number set at the factory). A lower bridge identifier results to a higher priority for the bridge, thus increasing its chance of being selected as the root bridge.
♦Root Path Cost The root path cost of a bridge is the sum of the path cost of the port from which a packet is forwarded and the root path costs of all the bridges the packet goes through. The root path cost of the root bridge is zero.
♦Bridge Priority This parameter can be set. The smaller the number you set, the higher the bridge priority is. The higher the bridge priority, the more chance the bridge has of becoming the root bridge.
Using the Console Interface | 43 |