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.
Given the following configuration 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 trunk will forward traffic for all VLANs except VLANs 100 through 200.
The 'switchport trunk allowed vlan except 100-200' command explicitly removes VLANs 100 through 200 from the allowed VLAN list on the trunk. All other VLANs (1-99 and 201-4094) remain permitted. This is the standard behavior of the 'except' keyword in Cisco IOS trunk configuration.
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 trunk will forward traffic for all VLANs except VLANs 100 through 200.
Why this is correct
Correct. The 'except' keyword excludes the specified range.
Related concept
Read the scenario before looking for a memorised answer.
✗
The trunk will only forward traffic for VLANs 100 through 200.
Why it's wrong here
Incorrect. That would be the effect if 'allowed vlan 100-200' was used without 'except'.
✗
The trunk will forward traffic for all VLANs.
Why it's wrong here
Incorrect. The 'except' clause removes VLANs 100-200 from the allowed list.
✗
The trunk will not forward any traffic because the allowed list is empty.
Why it's wrong here
Incorrect. The allowed list includes all VLANs except the specified range, so it is not empty.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the 'except' keyword to trap candidates who confuse it with 'add' or 'remove', leading them to think the trunk only forwards the specified range or that the allowed list becomes empty.
Detailed technical explanation
How to think about this question
The 'switchport trunk allowed vlan' command uses a list-based filter that is applied to the 802.1Q trunking protocol. The 'except' keyword is a shorthand to subtract a range from the default allowed VLAN set (all VLANs 1-4094, excluding reserved VLANs). A common real-world scenario is isolating a block of VLANs (e.g., guest or untrusted networks) from a trunk while allowing all other traffic, which avoids the need to list every permitted VLAN individually.
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 trunk will forward traffic for all VLANs except VLANs 100 through 200. — The 'switchport trunk allowed vlan except 100-200' command explicitly removes VLANs 100 through 200 from the allowed VLAN list on the trunk. All other VLANs (1-99 and 201-4094) remain permitted. This is the standard behavior of the 'except' keyword in Cisco IOS trunk configuration.
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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