- A
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan except 1
Correct because it sets the trunk, changes the native VLAN, and allows all VLANs except VLAN 1.
- B
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan remove 1
Why wrong: Incorrect because 'remove' is used to remove VLANs from the allowed list, but the syntax is 'switchport trunk allowed vlan remove 1', which would remove VLAN 1 from the current list, but the initial list includes all VLANs, so it would work, but the command is typically used in a different context. However, the 'except' command is more direct and less error-prone.
- C
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan 2-4094
Why wrong: Incorrect because it explicitly lists VLANs 2-4094, which excludes VLAN 1, but this is not as straightforward as using 'except' and could be considered less secure if VLANs are added later.
- D
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan none
Why wrong: Incorrect because 'none' blocks all VLANs, which is not the requirement.
350-401 VLANs and Trunking Practice Question
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.
A network engineer is configuring a new Cisco Catalyst 9300 switch to connect to an existing network. The uplink to the core switch is configured as a trunk. The engineer wants to ensure that all VLANs except VLAN 1 are allowed on the trunk, and that the native VLAN is set to VLAN 999. Which configuration should the engineer apply on the uplink interface?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan except 1
Option A is correct because the 'switchport trunk allowed vlan except 1' command explicitly permits all VLANs except VLAN 1 on the trunk, while the 'switchport trunk native vlan 999' command sets the native VLAN to 999, ensuring that untagged frames on the trunk belong to VLAN 999 instead of the default VLAN 1. This meets the requirement to exclude VLAN 1 from the allowed list and change the native VLAN.
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.
- ✓
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan except 1
Why this is correct
Correct because it sets the trunk, changes the native VLAN, and allows all VLANs except VLAN 1.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan remove 1
Why it's wrong here
Incorrect because 'remove' is used to remove VLANs from the allowed list, but the syntax is 'switchport trunk allowed vlan remove 1', which would remove VLAN 1 from the current list, but the initial list includes all VLANs, so it would work, but the command is typically used in a different context. However, the 'except' command is more direct and less error-prone.
- ✗
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan 2-4094
Why it's wrong here
Incorrect because it explicitly lists VLANs 2-4094, which excludes VLAN 1, but this is not as straightforward as using 'except' and could be considered less secure if VLANs are added later.
- ✗
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan none
Why it's wrong here
Incorrect because 'none' blocks all VLANs, which is not the requirement.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the difference between 'switchport trunk allowed vlan remove' and 'switchport trunk allowed vlan except', where candidates mistakenly think 'remove' is equivalent to 'except', but 'remove' only deletes a VLAN from the current list and requires the list to be pre-populated, while 'except' sets the list to all VLANs minus the specified ones in a single command.
Trap categories for this question
Command / output trap
Incorrect because 'remove' is used to remove VLANs from the allowed list, but the syntax is 'switchport trunk allowed vlan remove 1', which would remove VLAN 1 from the current list, but the initial list includes all VLANs, so it would work, but the command is typically used in a different context. However, the 'except' command is more direct and less error-prone.
Detailed technical explanation
How to think about this question
The 'switchport trunk allowed vlan except' command dynamically permits all VLANs except those specified, including reserved VLANs (1002-1005) that are not part of the normal 1-4094 range, whereas manually listing a range like 2-4094 may omit these reserved VLANs. Under the hood, the switch maintains a VLAN allowed list in the VLAN database, and the 'except' keyword modifies this list to include all VLANs except the excluded ones, ensuring compatibility with DTP and 802.1Q trunking behavior. In real-world scenarios, using 'except 1' is common when migrating from a default native VLAN to a non-default native VLAN to prevent VLAN 1 from being carried across the trunk, reducing security risks from VLAN hopping attacks.
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.
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VLANs and Trunking — study guide chapter
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FAQ
Questions learners often ask
What does this 350-401 question test?
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: switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan except 1 — Option A is correct because the 'switchport trunk allowed vlan except 1' command explicitly permits all VLANs except VLAN 1 on the trunk, while the 'switchport trunk native vlan 999' command sets the native VLAN to 999, ensuring that untagged frames on the trunk belong to VLAN 999 instead of the default VLAN 1. This meets the requirement to exclude VLAN 1 from the allowed list and change the native VLAN.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 24, 2026
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