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Difficulty: EasySTP Port States and PortFast Benefits

A network technician is configuring switch interfaces for end-user PCs on an enterprise access switch. Which classic 802.1D Spanning Tree Protocol (STP) port states are bypassed when Cisco STP PortFast is enabled on an access interface?

  1. Listening and LearningAnswer
  2. B
    Blocking and Listening
  3. C
    Learning and Forwarding
  4. D
    Blocking and Learning

Answer

Listening and Learning
Enabling PortFast on an access port allows the interface to bypass the 802.1D Listening and Learning states (which total 30 seconds of forward delay) and transition directly into the Forwarding state as soon as the link comes up.

Step-by-Step Solution

1
Recall standard 802.1D STP port state transition sequence
Standard 802.1D ports transition sequentially through Blocking -> Listening (15s forward delay) -> Learning (15s forward delay) -> Forwarding.
Listening determines topology structure and processes BPDUs, while Learning populates MAC address tables before frame forwarding.
2
Determine the effect of enabling PortFast on an access interface
PortFast allows access ports directly connected to end-user hosts to transition immediately from Blocking to Forwarding.
Bypassing the 30-second combined Listening (15s) and Learning (15s) delay prevents host application and DHCP discovery timeouts upon link initialization.

Key Concept

STP PortFast operational behavior and state transition bypass
Estimated Time:45s
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Topics

STP Port States and PortFast Benefits

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