This 350-401 practice question tests your understanding of vlans and trunking. 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.
Which two statements about VLAN trunking using IEEE 802.1Q are true? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The 802.1Q tag includes a 12-bit VLAN ID field.
Correct: A is true because 802.1Q inserts a 4-byte tag after the source MAC address, which includes a 12-bit VLAN ID (0-4095). B is true because the native VLAN is not tagged; frames on the native VLAN are sent untagged to maintain backward compatibility with devices that do not understand trunking. C is incorrect because the native VLAN can be any VLAN, not just VLAN 1; it defaults to VLAN 1 but can be changed. D is incorrect because the 802.1Q tag uses a TPID of 0x8100, not 0x88A8 (which is used for Q-in-Q). E is incorrect because 802.1Q supports up to 4094 usable VLANs (1-1001 and 1006-4094), not 4096.
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.
✓
The 802.1Q tag includes a 12-bit VLAN ID field.
Why this is correct
Correct because the 802.1Q header contains a 12-bit VLAN ID (VID) allowing up to 4094 VLANs.
Related concept
Access ports place end devices into a single VLAN.
✓
The native VLAN is not tagged on an 802.1Q trunk.
Why this is correct
Correct because 802.1Q leaves frames on the native VLAN untagged for interoperability.
Related concept
Access ports place end devices into a single VLAN.
✗
The native VLAN must always be VLAN 1.
Why it's wrong here
Incorrect because the native VLAN is configurable and can be any VLAN, though it defaults to VLAN 1.
✗
The 802.1Q tag uses a TPID value of 0x88A8.
Why it's wrong here
Incorrect because 0x88A8 is the TPID for Q-in-Q (802.1ad); 802.1Q uses 0x8100.
✗
802.1Q supports a maximum of 4096 VLANs.
Why it's wrong here
Incorrect because the 12-bit VID allows 4096 values, but VLANs 0 and 4095 are reserved, leaving 4094 usable VLANs.
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.
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 350-401 questions on switching, trunking, and access-port configuration.
VLANs and Trunking — This question tests VLANs and Trunking — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The 802.1Q tag includes a 12-bit VLAN ID field. — Correct: A is true because 802.1Q inserts a 4-byte tag after the source MAC address, which includes a 12-bit VLAN ID (0-4095). B is true because the native VLAN is not tagged; frames on the native VLAN are sent untagged to maintain backward compatibility with devices that do not understand trunking. C is incorrect because the native VLAN can be any VLAN, not just VLAN 1; it defaults to VLAN 1 but can be changed. D is incorrect because the 802.1Q tag uses a TPID of 0x8100, not 0x88A8 (which is used for Q-in-Q). E is incorrect because 802.1Q supports up to 4094 usable VLANs (1-1001 and 1006-4094), not 4096.
What should I do if I get this 350-401 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 350-401 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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