This 350-401 practice question tests your understanding of vlans and trunking. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Examine the following configuration snippet on a Cisco IOS switch:
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The interface will immediately forward traffic without any spanning-tree delay.
The `spanning-tree portfast` command on an access port configured with `switchport mode access` and `switchport access vlan 50` causes the interface to bypass the normal spanning-tree listening and learning states. This allows the port to transition directly to the forwarding state, enabling immediate traffic forwarding without the usual 30-second delay (15 seconds for listening, 15 seconds for learning) associated with Rapid Spanning Tree Protocol (RSTP) or the 50-second delay with classic STP (802.1D).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The interface will immediately forward traffic without any spanning-tree delay.
Why this is correct
Correct. PortFast enables immediate forwarding, reducing the initial delay.
Related concept
Read the scenario before looking for a memorised answer.
✗
The interface will participate in trunking and forward multiple VLANs.
Why it's wrong here
Incorrect. The 'switchport mode access' command makes it an access port, not a trunk.
✗
The interface will still go through listening and learning states before forwarding.
The interface will only forward traffic for VLAN 1.
Why it's wrong here
Incorrect. The access VLAN is set to 50, so it forwards traffic for VLAN 50.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that `spanning-tree portfast` only applies to trunk ports or that it still requires the listening/learning states, when in fact it is designed specifically to bypass those states on access ports (or trunk ports with the `spanning-tree portfast trunk` variant).
Trap categories for this question
Command / output trap
Incorrect. The 'switchport mode access' command makes it an access port, not a trunk.
Detailed technical explanation
How to think about this question
PortFast is a Cisco proprietary enhancement that works with both classic STP (802.1D) and RSTP (802.1w). When enabled, it places the port in an STP edge port role, which immediately transitions to forwarding. However, if a BPDU is received on a PortFast-enabled port, the port loses its edge status and reverts to normal STP operation, potentially causing a temporary loop. In real-world scenarios, PortFast is commonly used on ports connecting to end devices like workstations or printers to avoid connectivity delays during boot-up or link flapping.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
VLANs and Trunking — This question tests VLANs and Trunking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The interface will immediately forward traffic without any spanning-tree delay. — The `spanning-tree portfast` command on an access port configured with `switchport mode access` and `switchport access vlan 50` causes the interface to bypass the normal spanning-tree listening and learning states. This allows the port to transition directly to the forwarding state, enabling immediate traffic forwarding without the usual 30-second delay (15 seconds for listening, 15 seconds for learning) associated with Rapid Spanning Tree Protocol (RSTP) or the 50-second delay with classic STP (802.1D).
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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