- A
Layer 1 (Physical)
Why wrong: Physical layer does not understand VLAN tags.
- B
Layer 3 (Network)
Why wrong: Layer 3 operates on packets, not frames.
- C
Layer 2 (Data Link)
VLAN tagging is a Layer 2 function using IEEE 802.1Q.
- D
Layer 4 (Transport)
Why wrong: Transport layer is above switching.
Question 896 of 1,000
200-901 Network Fundamentals Practice Question
This 200-901 practice question tests your understanding of network fundamentals. 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 configures a switch port to belong to VLAN 10. Which OSI layer is primarily involved in VLAN tagging?
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
✓
Layer 2 (Data Link)
VLANs operate at Layer 2 (Data Link) by adding tags to Ethernet frames.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Layer 1 (Physical)
Why it's wrong here
Physical layer does not understand VLAN tags.
- ✗
Layer 3 (Network)
Why it's wrong here
Layer 3 operates on packets, not frames.
- ✓
Layer 2 (Data Link)
- ✗
Layer 4 (Transport)
Why it's wrong here
Transport layer is above switching.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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.
Visual reference
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-901 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 200-901 question test?
Network Fundamentals — This question tests Network Fundamentals — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Layer 2 (Data Link) — VLANs operate at Layer 2 (Data Link) by adding tags to Ethernet frames.
What should I do if I get this 200-901 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-901 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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Last reviewed: Jul 4, 2026
This 200-901 practice question is part of Courseiva's free Cisco 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 200-901 exam.
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