This N10-009 practice question tests your understanding of network implementation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 technician needs to connect two switches to support multiple VLANs between them. The technician wants to use a single link to carry traffic for all VLANs. Which protocol should be used to tag frames with VLAN information?
802.1Q
Correct. 802.1Q is the standard for VLAN tagging on trunk links.
802.1X
Why wrong: 802.1X is used for authentication, not VLAN tagging.
802.11
Why wrong: 802.11 is the wireless standard, not used for VLAN tagging on wired links.
802.3
Why wrong: 802.3 defines Ethernet framing but does not support VLAN tagging without 802.1Q.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
802.1Q
802.1Q is the IEEE standard for VLAN tagging, which inserts a 4-byte tag into the Ethernet frame header to identify the VLAN membership of the frame. This allows a single trunk link between two switches to carry traffic for multiple VLANs by tagging each frame with its corresponding VLAN ID (1-4094).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Common exam traps
The trap here is that candidates often confuse 802.1Q (VLAN tagging) with 802.1X (port authentication) because of the similar numbering, or they assume 802.3 handles VLANs since it is the base Ethernet standard.
Detailed technical explanation
802.1Q tagging works by inserting a 4-byte tag between the Source MAC and EtherType fields, which includes a 12-bit VLAN ID (VID) allowing up to 4094 VLANs (VIDs 0 and 4095 are reserved). On Cisco switches, the trunk must be configured with the 'switchport mode trunk' command and the native VLAN (typically VLAN 1) is left untagged, which can cause VLAN hopping if not secured properly.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
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FAQ
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
The correct answer is: 802.1Q — 802.1Q is the IEEE standard for VLAN tagging, which inserts a 4-byte tag into the Ethernet frame header to identify the VLAN membership of the frame. This allows a single trunk link between two switches to carry traffic for multiple VLANs by tagging each frame with its corresponding VLAN ID (1-4094).
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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