Which of the following is true regarding RSTP costs?

The correct answer is that cost values decrease as the bandwidth increases. In the context of Rapid Spanning Tree Protocol (RSTP), the cost of a link is inversely proportional to its bandwidth, which means that higher bandwidth links will have lower cost values. This is crucial because when RSTP is determining the best path for traffic, it will favor the links with lower costs, effectively choosing higher bandwidth options wherever available.

For instance, if you have a 1 Gbps link and a 10 Mbps link, the cost of the 10 Mbps link would be higher than that of the 1 Gbps link, leading RSTP to prefer the 1 Gbps link for data transmission. This mechanism allows RSTP to optimize network performance by utilizing the most efficient paths.

In contrast, the other choices do not align with how RSTP costs are structured. Cost values are not fixed regardless of link type; they are actually determined based on the link's bandwidth. Additionally, cost values cannot increase with increased bandwidth, as this would contradict the fundamental design of RSTP, which emphasizes the use of faster links for better network efficiency. Lastly, not all link types have the same cost; the costs vary based on the bandwidth and characteristics