Quick Answer
The answer is VLAN 1. This is the default native VLAN on a Cisco switch trunk port because, per the IEEE 802.1Q standard, all switch ports are assigned to VLAN 1 by default, and the native VLAN is the one that carries untagged traffic across a trunk link. On a Cisco trunk, frames belonging to the native VLAN are not tagged with a VLAN ID, which is a critical distinction for understanding how trunking and VLAN segmentation work. On the ENCOR 350-401 exam, this concept tests your knowledge of Layer 2 switching fundamentals and often appears in questions about trunk configuration or troubleshooting mismatched native VLANs. A common trap is assuming the default native VLAN is something other than VLAN 1, such as VLAN 1001 or a user-created VLAN, but Cisco’s default remains VLAN 1 unless explicitly changed with the switchport trunk native vlan command. Memory tip: think “One is the default native” — VLAN 1 is always the starting point for untagged traffic on a trunk.
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.
What is the default native VLAN on a Cisco switch trunk port?
VLAN 1
Correct. The default native VLAN is VLAN 1.
VLAN 0
Why wrong: Incorrect. VLAN 0 is not a valid VLAN number.
VLAN 1002
Why wrong: Incorrect. VLAN 1002 is one of the default VLANs (FDDI), but not the native VLAN.
VLAN 4095
Why wrong: Incorrect. VLAN 4095 is reserved and not used as a native VLAN.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VLAN 1
The default native VLAN on a Cisco switch trunk port is VLAN 1. The native VLAN is the VLAN that carries untagged traffic over a trunk link, and by default, all switch ports (including trunk ports) belong to VLAN 1. This is defined in the IEEE 802.1Q standard, which specifies that frames on the native VLAN are not tagged with a VLAN ID.
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.
VLAN 1
Why this is correct
Correct. The default native VLAN is VLAN 1.
Related concept
Read the scenario before looking for a memorised answer.
VLAN 0
Why it's wrong here
Incorrect. VLAN 0 is not a valid VLAN number.
VLAN 1002
Why it's wrong here
Incorrect. VLAN 1002 is one of the default VLANs (FDDI), but not the native VLAN.
VLAN 4095
Why it's wrong here
Incorrect. VLAN 4095 is reserved and not used as a native VLAN.
Common exam traps
Cisco often tests the misconception that the native VLAN is always VLAN 1 by default, but the trap is that candidates may confuse it with the management VLAN (also often VLAN 1) or assume that changing the native VLAN is required for trunking to work.
Detailed technical explanation
Under the hood, the native VLAN concept is critical for backward compatibility with devices that do not understand 802.1Q tagging; mismatched native VLANs on a trunk can cause VLAN hopping or connectivity issues. In a real-world scenario, if you change the native VLAN to something other than 1 (e.g., using 'switchport trunk native vlan 10'), you must ensure both ends of the trunk match, or the switch will drop or misdirect untagged frames. Cisco also recommends changing the native VLAN from 1 as a security best practice to prevent VLAN hopping attacks.
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.
What to study next
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FAQ
VLANs and Trunking — This question tests VLANs and Trunking — Read the scenario before looking for a memorised answer..
The correct answer is: VLAN 1 — The default native VLAN on a Cisco switch trunk port is VLAN 1. The native VLAN is the VLAN that carries untagged traffic over a trunk link, and by default, all switch ports (including trunk ports) belong to VLAN 1. This is defined in the IEEE 802.1Q standard, which specifies that frames on the native VLAN are not tagged with a VLAN ID.
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 24, 2026
This 350-401 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 350-401 exam.
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