Cisco Certified Network Associate (CCNA) Practice Exam

What is the default STP bridge priority number?

1. 16,384

2. 32,768

3. 64,000

4. 48,576

The correct answer is: 32,768

The default Spanning Tree Protocol (STP) bridge priority number is set to 32,768. This value is significant because it determines the likelihood of a switch becoming the root bridge in a spanning tree topology. The bridge priority is a component of the Bridge ID, which is used to elect the root bridge based on the lowest Bridge ID value. In the context of STP, if two switches have the same bridge priority, the tie is broken by their MAC addresses, with the switch having the lower MAC address becoming the root bridge. Understanding this priority value is crucial for network design and troubleshooting, ensuring efficient loop avoidance within Ethernet networks. It's important to note that while administrators can modify the bridge priority to influence which switch becomes the root bridge, the default value remains at 32,768 unless changed manually.