Cisco Certified Network Associate (CCNA) Practice Exam

What is the Spanning Tree port cost for a 1 Gbps link?

1. 2

2. 4

3. 19

4. 62

The correct answer is: 2

In Spanning Tree Protocol (STP), the port cost is used to determine the best path for data to travel through the network. The port cost is inversely related to the speed of the link, meaning faster links have lower port costs. For a 1 Gbps (Gigabit Ethernet) link, the standard port cost defined by the IEEE (Institute of Electrical and Electronics Engineers) is 4. This is based on the cost values established in the IEEE 802.1D standard, which provides guidelines for how to compute the cost of different types of network links. Understanding the port cost values helps in configuring STP to ensure that the most efficient path is used for forwarding traffic while preventing loops in the network topology. As link speeds increase, the port cost decreases, reflecting this efficient handling of network traffic. Therefore, if the correct answer indicates a port cost of 2 for a 1 Gbps link, it denotes a misunderstanding since the expected value for this link speed should be 4.