- A
The IP address of the router interface must be in the same subnet as the management VLAN
Why wrong: The router's IP address on the trunk interface is not necessarily tied to the management VLAN; it can be associated with any VLAN subinterface.
- B
The subinterface encapsulation must match the switch's native VLAN default
Why wrong: Encapsulation on subinterfaces matches VLAN IDs, not the native VLAN. The native VLAN is untagged and handled by the main interface or a specific subinterface.
- C
The native VLAN on the router subinterface must be consistent with the switch's native VLAN
Both ends of a trunk must agree on the native VLAN, typically VLAN 1 by default, but it can be changed. Inconsistency can cause miscommunication or security risks.
- D
The router must be configured with inter-VLAN routing static routes
Why wrong: Inter-VLAN routing can be done directly on the router without static routes if the router has interfaces in each VLAN; a trunk link does not require static routes for the trunk itself.
Quick Answer
The answer is that the native VLAN on the router subinterface must be consistent with the switch's native VLAN. This is required because on an 802.1Q trunk, the native VLAN is the only VLAN whose frames traverse the link untagged; if the router subinterface expects a different native VLAN, it will either drop those untagged frames or misclassify them into the wrong VLAN, breaking communication for that entire VLAN. On the CompTIA Network+ N10-009 exam, this concept tests your understanding of trunking and VLAN tagging, often appearing in a scenario where a router-on-a-stick configuration fails because the native VLANs are mismatched. A common trap is assuming all frames are tagged, but the native VLAN is always sent untagged, so both ends must agree. Remember the memory tip: "Native must match, or traffic will catch"—if the native VLAN IDs don't align, untagged traffic gets lost.
N10-009 Network Implementation Practice Question
This N10-009 practice question tests your understanding of network implementation. 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 administrator is configuring a trunk link between a switch and a router to support multiple VLANs. The switch's trunk port is set to dot1q encapsulation. Which configuration must match on the router to ensure proper communication?
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
The native VLAN on the router subinterface must be consistent with the switch's native VLAN
Option C is correct because the native VLAN on the router subinterface must match the switch's native VLAN to ensure untagged frames are handled consistently. On a dot1q trunk, the native VLAN is the only VLAN whose frames are sent untagged; if the router expects a different native VLAN, it will drop or misclassify those frames, breaking communication for that 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.
- ✗
The IP address of the router interface must be in the same subnet as the management VLAN
- ✗
The subinterface encapsulation must match the switch's native VLAN default
Why it's wrong here
Encapsulation on subinterfaces matches VLAN IDs, not the native VLAN. The native VLAN is untagged and handled by the main interface or a specific subinterface.
- ✓
The native VLAN on the router subinterface must be consistent with the switch's native VLAN
Why this is correct
Both ends of a trunk must agree on the native VLAN, typically VLAN 1 by default, but it can be changed. Inconsistency can cause miscommunication or security risks.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The router must be configured with inter-VLAN routing static routes
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'native VLAN' with 'default VLAN' or think the encapsulation type (dot1q) alone is sufficient, overlooking the critical requirement that the native VLAN must be explicitly matched on both sides of the trunk.
Detailed technical explanation
How to think about this question
Under the hood, the IEEE 802.1Q standard reserves VLAN 1 as the default native VLAN, but administrators often change it to a non-default VLAN (e.g., VLAN 99) to avoid security risks like VLAN hopping. In a router-on-a-stick setup, the 'encapsulation dot1q <vlan-id> native' command on the subinterface tells the router to treat that VLAN as untagged; if the switch's native VLAN is 99 and the router's subinterface for VLAN 99 lacks the 'native' keyword, the router will expect a dot1q tag on those frames, causing a mismatch.
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
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The native VLAN on the router subinterface must be consistent with the switch's native VLAN — Option C is correct because the native VLAN on the router subinterface must match the switch's native VLAN to ensure untagged frames are handled consistently. On a dot1q trunk, the native VLAN is the only VLAN whose frames are sent untagged; if the router expects a different native VLAN, it will drop or misclassify those frames, breaking communication for that VLAN.
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.
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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