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.
Consider the following configuration on a Cisco IOS-XE 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 operate as an 802.1Q trunk, and untagged frames will be associated with VLAN 1.
The configuration sets the interface to 802.1Q trunking mode and explicitly defines VLAN 1 as the native VLAN. On an 802.1Q trunk, the native VLAN is the VLAN to which untagged frames are assigned when received on the trunk port. Since VLAN 1 is the default native VLAN and is explicitly configured here, untagged frames will be associated with VLAN 1, allowing them to traverse the trunk without an 802.1Q tag.
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 operate as an 802.1Q trunk, and untagged frames will be associated with VLAN 1.
Why this is correct
Correct. The native VLAN is 1, so untagged frames belong to VLAN 1.
Related concept
Read the scenario before looking for a memorised answer.
✗
The interface will operate as an ISL trunk.
Why it's wrong here
Incorrect. The encapsulation is explicitly set to dot1q, not ISL.
✗
The interface will drop all untagged frames.
Why it's wrong here
Incorrect. Untagged frames are accepted on the native VLAN.
✗
The interface will only forward traffic for VLAN 1.
Why it's wrong here
Incorrect. By default, a trunk forwards all VLANs unless restricted by an allowed VLAN list.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a trunk port drops untagged frames or that the native VLAN is only for management traffic, when in fact untagged frames are always associated with the native VLAN on an 802.1Q trunk.
Detailed technical explanation
How to think about this question
In 802.1Q trunking, the native VLAN is a critical concept for backward compatibility with devices that do not understand VLAN tagging. When a trunk port receives an untagged frame, it is automatically placed into the native VLAN, and when forwarding frames from the native VLAN, the switch typically sends them untagged (unless configured otherwise with 'switchport trunk native vlan tag'). This behavior is defined in IEEE 802.1Q, and misconfiguration of the native VLAN can lead to VLAN hopping attacks if the native VLAN is not pruned or changed from the default.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
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 operate as an 802.1Q trunk, and untagged frames will be associated with VLAN 1. — The configuration sets the interface to 802.1Q trunking mode and explicitly defines VLAN 1 as the native VLAN. On an 802.1Q trunk, the native VLAN is the VLAN to which untagged frames are assigned when received on the trunk port. Since VLAN 1 is the default native VLAN and is explicitly configured here, untagged frames will be associated with VLAN 1, allowing them to traverse the trunk without an 802.1Q tag.
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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