200-301 Question 225
Single answerYou are configuring a network with several access layer switches connected to end-user devices. One of the switches frequently experiences a 30-50 second delay before forwarding traffic after a port is connected to a device. To resolve this issue, you decide to enable PortFast. Which of the following is a characteristic of PortFast and its behavior in this scenario?
- A
PortFast immediately transitions the port to the forwarding state, bypassing the listening and learning states of STP.
- B
PortFast disables Spanning Tree Protocol (STP) on the port to improve convergence time.
- C
PortFast should only be enabled on trunk ports to speed up the forwarding process.
- D
Enabling PortFast on an access port helps prevent topology changes caused by end-user device connections.
Show answer and explanation
Correct answer: A
Explanation
PortFast is a feature of Spanning Tree Protocol (STP) that is used to immediately transition an access port to the forwarding state when a device is connected. This eliminates the standard 30-50 second delay caused by the STP listening and learning states, which is particularly useful for end-user devices. However, PortFast should only be enabled on access ports and not on trunk ports or switch-to-switch links to avoid network loops.
- A. Correct.
Correct. PortFast is designed to immediately transition a port to the forwarding state, bypassing the listening and learning states of the Spanning Tree Protocol, which eliminates the delay for end-user devices.
- B. Incorrect.
Incorrect. PortFast does not disable STP on the port; it only changes the behavior to optimize convergence time for specific scenarios. STP is still operational to prevent loops.
- C. Incorrect.
Incorrect. PortFast is not recommended on trunk ports because it is specifically intended for access ports connected to end-user devices, not links between switches.
- D. Incorrect.
Incorrect. While PortFast reduces the impact of topology changes caused by end-user devices, its primary purpose is to eliminate the delay in forwarding traffic on access ports.