What is Spanning Tree?

In computer networking, a spanning tree is a tree data structure that is used to represent the connectivity of a network that has multiple interconnected devices. It is used to ensure that there are no loops in the network, and to identify the shortest path between devices. The spanning tree algorithm is used to create a tree of the network topology, and the resulting tree is used to prevent loops from forming in the network by disabling certain connections.

In a spanning tree, all of the devices in the network are connected, but some of the connections are disabled to prevent loops. This allows data to be transmitted through the network without the risk of endless loops forming. The spanning tree algorithm is used to calculate the shortest path between devices, and the resulting tree is used to transmit data between devices in the network.

Spanning tree is used in many different types of networks, including local area networks (LANs), wide area networks (WANs), and virtual LANs (VLANs). It is an important tool for ensuring the reliability and efficiency of network communication.

The spanning tree algorithm was developed by Radia Perlman in the 1980s, and it has become a standard feature of networking devices such as switches and routers.

The spanning tree algorithm works by electing a root device, which is typically a central device such as a switch or router. The root device sends out a special type of message called a "root bridge identification" message, which is used to identify the root device to the other devices in the network.

The other devices in the network respond to the root bridge identification message by sending messages back to the root device. These messages contain information about the device's own connections to the network, as well as the distance (measured in hops) between the device and the root device.

The root device uses this information to calculate the shortest path to each device in the network, and creates a tree structure that represents the connectivity of the network. The resulting tree is called the "spanning tree."

In the spanning tree, some of the connections between devices are disabled to prevent loops from forming. These disabled connections are called "blocked ports." When a device receives data, it checks the spanning tree to determine the shortest path to the destination device, and sends the data along that path.

If the network topology changes, the spanning tree algorithm is used to recalculate the shortest path and update the tree accordingly. This ensures that the network continues to operate efficiently and without loops.