Spanning Tree protocol is a loop prevention mechanism in a bridged LAN. Every STP topology has its own root bridge, which determines how STP topology is calculated. The role of the root bridge is to act as a reference point in the network, so that all other switches can determine, how far each of their ports is from the root bridge. The port, which has the lowest path cost, is placed into a forwarding state. All other ports, that can lead to the root bridge, are blocked. Ports in the switching topology, which lead away from the Root Bridge, remain forwarding. You can recall STP operations reading the following article: “Multiple Spanning Tree Protocol on Huawei switch“.
How does the root bridge election process work?
The root bridge for each STP instance is determined by the bridge ID. The bridge ID consists of a configurable bridge priority and the MAC address of the bridge:
[Huawei]display stp -------[CIST Global Info][Mode MSTP]------- CIST Bridge :32768.4c1f-ccd4-1c03