Which of the following statements correctly describe features of Rapid Spanning Tree Protocol (RSTP) compared to legacy STP? (Select all that apply.)
Correct Answer: A,B,C
Detailed Explanation: Spanning Tree Protocol (STP) is essential for preventing loops in networks that include redundant links. Traditional STP (IEEE 802.1D) can be slow to converge—often taking up to 30–50 seconds—when the network topology changes. Rapid Spanning Tree Protocol (RSTP), defined by IEEE 802.1w, was developed to overcome these limitations, providing quicker network reconvergence and improved performance. A. Faster Convergence: RSTP was designed to minimize downtime when a link fails or a new device is introduced. By streamlining the process of detecting topology changes and reassigning port roles, RSTP significantly reduces convergence times. In many cases, convergence can occur within a few seconds. This improvement is crucial for time-sensitive applications (like VoIP or real-time video) that cannot tolerate long outages or delays. B. New Port Roles: RSTP introduces additional port roles to provide a more robust and efficient approach to managing redundant links. In legacy STP, ports are typically assigned roles such as root port, designated port, or blocked port. RSTP adds roles like alternate and backup ports: Alternate Port: A port that offers an alternative path to the root bridge; it can rapidly transition to forwarding if the primary (root) port fails. Backup Port: A port that provides a redundant connection on a shared segment, used when the designated port is unavailable. These new roles allow the protocol to react more quickly to changes, ensuring that alternate paths are already in place and ready to take over. C. Discarding State: In traditional STP, ports that are not selected to forward frames enter a blocking state to avoid loops. RSTP streamlines this by eliminating the “blocking” state and replacing it with a “discarding” state. Although similar in function—preventing the transmission of user data—the discarding state in RSTP is part of a faster transition process. Ports in the discarding state are still actively monitored for changes; if a change is detected, they can transition rapidly into the forwarding state. This shift is part of what enables RSTP’s faster convergence. D. Manual Reconfiguration (Incorrect): One of the key benefits of RSTP is that it is designed to react automatically to topology changes without manual intervention. The protocol’s built-in mechanisms for rapid detection and port role adjustment mean that administrators do not need to manually reconfigure the network when a topology change occurs. Manual intervention would negate many of the operational improvements provided by RSTP. Conclusion: In summary, RSTP offers faster convergence (Option A), introduces new port roles such as alternate and backup (Option B), and replaces the traditional blocking state with a discarding state (Option C) to improve responsiveness. It is designed for automatic recovery without the need for manual reconfiguration, making Option D incorrect. These enhancements contribute to a more resilient and efficient network, particularly important in environments where downtime must be minimized.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.