STP – Spanning Tree Protocol. The spanning tree protocol was introduced to network administrators as a way to correct the mistakes and downfalls that occurred during the set up of network bridges on a network. Basically, what STP helps for is correcting/fixing a loop on a network and also deals with network changes and failures.

Now, before continuing about Spanning Tree protocol (which is all about bridges) it’s important to notice the difference between bridges and switches. STP was introduces before switches existed. Switch can hold up from 12 to 48 ports, while a bridge can hold up to 4 or 8 ports.

Switches are mainly more practical then bridge. Now, Spanning Tree protocol works as a Layer 2 protocol. What does that mean? Means that this protocol passes data back and forth through a network so it can find how the switches work and how the switches are organized and then creates a logical tree, thus the name Spanning TREE.

If you follow the process of data transfer closely, you will know exactly how the switches are interconnected and how they functionate. These information, the protocol builds by sending out network packets called units or BDU’s (Bridge Protocol Data Units).

The most important thing about these units is that it gives the protocol and opportunity to create the network topology of the switches.