What is the RSTP port cost for a 1 Gbps link?

The correct answer for the RSTP port cost for a 1 Gbps link is 20,000. In Rapid Spanning Tree Protocol (RSTP), the port cost is a value used to determine the best path for data to travel across a network. The port cost is inversely proportional to the bandwidth of the link; the higher the bandwidth, the lower the cost.

For Ethernet links, the standard costs are defined in the IEEE 802.1D specification and have been revised in subsequent documents. Specifically, the cost is calculated based on the speed of the link. For a 1 Gbps link, the cost is set at 20,000. This encourages the switch to prefer higher-bandwidth links when selecting the best path.

Other values listed, such as 2,000, 200, and 20, correspond to different bandwidth links. For example, a 100 Mbps link would typically have a port cost of 200, while 10 Mbps would be set at 20. These cost values facilitate the Spanning Tree Protocol's decision-making process regarding which links should be used for forwarding traffic and which should be blocked to prevent loops in the network. Understanding these port costs is vital for network design and optimization.