- A
show vlan
Why wrong: 'show vlan' displays the VLAN database and which ports are in which VLANs, but it does not show which VLANs are allowed on a trunk interface.
- B
show interfaces trunk
'show interfaces trunk' lists trunk interfaces, their mode, encapsulation, and the allowed VLAN list. If the required VLAN is not in the allowed list, traffic for that VLAN will not pass over the trunk.
- C
show mac address-table
Why wrong: 'show mac address-table' displays MAC addresses learned on switch ports. It can help identify connectivity issues on specific VLANs but does not verify trunk configuration.
- D
show ip route
Why wrong: 'show ip route' displays the router's routing table. While routing may be affected if the VLAN is not trunked, this command does not show trunking details.
N10-009 Network Troubleshooting Practice Question
This N10-009 practice question tests your understanding of network troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
After replacing a faulty switch, several users in the same VLAN report that they cannot communicate with the server that is on a different subnet. The switch is connected to the router via a trunk port. Which command should the administrator run on the router to verify that the VLAN is allowed on the trunk?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"which command"Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
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
show interfaces trunk
The `show interfaces trunk` command displays which VLANs are allowed on each trunk port. Since the switch is connected to the router via a trunk, this command verifies whether the VLAN of the affected users is permitted on that trunk. If the VLAN is missing from the allowed list, traffic to the server on a different subnet will be dropped at the router interface.
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.
- ✗
show vlan
- ✓
show interfaces trunk
Why this is correct
'show interfaces trunk' lists trunk interfaces, their mode, encapsulation, and the allowed VLAN list. If the required VLAN is not in the allowed list, traffic for that VLAN will not pass over the trunk.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
show mac address-table
Why it's wrong here
'show mac address-table' displays MAC addresses learned on switch ports. It can help identify connectivity issues on specific VLANs but does not verify trunk configuration.
- ✗
show ip route
Why it's wrong here
'show ip route' displays the router's routing table. While routing may be affected if the VLAN is not trunked, this command does not show trunking details.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse `show vlan` (which shows local switch VLANs) with `show interfaces trunk` (which shows VLAN filtering on the trunk), leading them to pick A when the real issue is trunk permission, not VLAN existence.
Trap categories for this question
Command / output trap
'show vlan' displays the VLAN database and which ports are in which VLANs, but it does not show which VLANs are allowed on a trunk interface.
Detailed technical explanation
How to think about this question
On a Cisco router, trunking uses subinterfaces with 802.1Q encapsulation; the `show interfaces trunk` command reveals the allowed VLAN list, native VLAN, and trunking status. A common real-world scenario is when a new VLAN is added but not explicitly permitted on the trunk, causing all traffic from that VLAN to be silently dropped at the router, even though the switch port is correctly configured.
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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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Troubleshooting — This question tests Network Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: show interfaces trunk — The `show interfaces trunk` command displays which VLANs are allowed on each trunk port. Since the switch is connected to the router via a trunk, this command verifies whether the VLAN of the affected users is permitted on that trunk. If the VLAN is missing from the allowed list, traffic to the server on a different subnet will be dropped at the router interface.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This N10-009 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the N10-009 exam.
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