Cisco switches have been the preferred network devices in businesses for many years now. They offer advanced features and are reliable. One of the essential features of Cisco switches is the Spanning Tree Protocol. The Spanning Tree Protocol is responsible for preventing network loops and ensuring that the network is fault-tolerant. It is the magic behind the reliability of Cisco switches. In this article, we will demystify the magic of the Spanning Tree Algorithm in Cisco switches.
What is the Spanning Tree Protocol?
The Spanning Tree Protocol is a layer 2 protocol used to prevent network loops. It ensures that there is only one active path between any two network nodes. A network loop occurs when there are multiple paths between two nodes, and traffic is continually circulating around the loop, causing congestion. By default, Cisco switches enable the Spanning Tree Protocol, which ensures that there is only one active path between the switches.
How Does the Spanning Tree Algorithm Work?
The Spanning Tree Algorithm works by electing one switch as the root bridge of the network. The root bridge is the switch with the lowest bridge ID. The bridge ID is a combination of the switch’s priority and MAC address. Once the root bridge is elected, it sends out configuration messages to all switches in the network. The switches then use this information to determine the best path to the root bridge.
The Spanning Tree Algorithm uses the following steps to prevent network loops:
1. Elect the root bridge: As mentioned earlier, the switch with the lowest bridge ID becomes the root bridge of the network.
2. Elect the root port: The root port is the switch port that provides the shortest path to the root bridge. Each non-root switch determines the root port by comparing the cost of reaching the root bridge through each of its ports.
3. Elect the designated port: The designated port is the switch port that provides the shortest path from the non-root switch to the root bridge. Each non-root switch determines the designated port by comparing the cost of reaching the root bridge through its ports and the cost of reaching the root bridge through the path provided by the root port of its neighbor.
4. Disable redundant ports: Once the root and designated ports are elected, all other ports are disabled to prevent network loops.
The Spanning Tree Algorithm ensures that there is only one active path between the switches, and the network is fault-tolerant. If a link fails, the Spanning Tree Algorithm recalculates the network topology and finds a new path from the non-root switch to the root bridge.
Conclusion
The Spanning Tree Algorithm is the magic behind the reliability of Cisco switches. It ensures that there is only one active path between the switches, preventing network loops and making the network fault-tolerant. The Spanning Tree Algorithm uses a set of rules to elect the root bridge, root port, and designated port. Once these ports are elected, all other ports are disabled to prevent network loops. By demystifying the Spanning Tree Algorithm, network administrators can better understand how it works and optimize their network for reliability and performance.