CCNA Switching and Network Access Practice Question
On an 802.1Q trunk, which VLAN is sent untagged by default on many Cisco switches unless changed?
⚠ Common exam trap
Be cautious not to confuse commonly used VLANs in practice with the default native VLAN set by Cisco.
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
✓
VLAN 1
On many Cisco platforms, VLAN 1 is the default native VLAN. Native VLAN traffic is sent untagged unless the native VLAN is changed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
VLAN 10
Why it's wrong here
VLAN 10 is not the native VLAN by default; it is an ordinary data VLAN. On an 802.1Q trunk, a frame belonging to VLAN 10 would include a 4-byte 802.1Q tag with VLAN ID 10, making it a tagged frame. Only the default native VLAN, which is almost always VLAN 1 on Cisco platforms, remains untagged.
When this WOULD be correct
If the exam question specified a scenario where VLAN 10 was explicitly configured as the native VLAN on a specific switch or in a particular network design, then it would be the correct answer. For example, a question could state that a network administrator has changed the default native VLAN to VLAN 10.
- ✗
VLAN 20
Why it's wrong here
Selecting VLAN 20 as the untagged VLAN would require manual configuration of the switchport trunk native vlan command. The factory-default state does not assign any arbitrary VLAN like 20 to the native role; it reserves that function for VLAN 1. Therefore, unless an administrator explicitly changes the native VLAN, VLAN 20 frames will always be tagged on the trunk.
When this WOULD be correct
If the exam question specified a scenario where VLAN 20 was explicitly configured as the native VLAN on a particular Cisco switch, then VLAN 20 would be the correct answer. For example, a question could ask which VLAN is untagged on a switch where the administrator has changed the default native VLAN to 20.
- ✓
VLAN 1
Why this is correct
By default, Cisco switches configure VLAN 1 as the native VLAN on an 802.1Q trunk. Frames in the native VLAN are transmitted without a VLAN tag, while all other VLANs carry a 802.1Q tag. This default behavior ensures that control-plane traffic like CDP, VTP, and DTP, which typically run on VLAN 1, can traverse the trunk without tagging.
- ✗
The highest configured VLAN
Why it's wrong here
The highest configured VLAN has no relationship to 802.1Q native VLAN behavior. Native VLAN selection is based on a fixed default (VLAN 1) or explicit administrative configuration, not on the numeric maximum or any dynamic property of the VLAN list. Even if VLAN 4000 is the highest VLAN, it would still be tagged unless configured as native.
When this WOULD be correct
In a different question asking which VLAN is used as the native VLAN when a switch is configured to use the highest VLAN number as the native VLAN, option D would be correct. For instance, if a switch has VLANs 1 through 50 configured and the question specifies that the highest VLAN is set as the native VLAN, then VLAN 50 would be the answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓VLAN 1Correct answer▾
Why this is correct
By default, Cisco switches configure VLAN 1 as the native VLAN on an 802.1Q trunk. Frames in the native VLAN are transmitted without a VLAN tag, while all other VLANs carry a 802.1Q tag. This default behavior ensures that control-plane traffic like CDP, VTP, and DTP, which typically run on VLAN 1, can traverse the trunk without tagging.
✗VLAN 10Wrong answer — click to see why▾
Why this is wrong here
VLAN 10 is not the default untagged VLAN on Cisco switches; instead, VLAN 1 is typically used for this purpose unless configured otherwise. Therefore, selecting VLAN 10 would be incorrect in the context of the question.
★ When this WOULD be the correct answer
If the exam question specified a scenario where VLAN 10 was explicitly configured as the native VLAN on a specific switch or in a particular network design, then it would be the correct answer. For example, a question could state that a network administrator has changed the default native VLAN to VLAN 10.
Why candidates choose this
Candidates might choose VLAN 10 due to familiarity with common VLAN configurations or because they recall that VLAN 10 is often used in various network setups, leading to confusion about default settings.
✗VLAN 20Wrong answer — click to see why▾
Why this is wrong here
VLAN 20 is not the default untagged VLAN on Cisco switches; instead, VLAN 1 is typically sent untagged on 802.1Q trunks unless configured otherwise. Therefore, selecting VLAN 20 does not align with the standard behavior of Cisco switch configurations.
★ When this WOULD be the correct answer
If the exam question specified a scenario where VLAN 20 was explicitly configured as the native VLAN on a particular Cisco switch, then VLAN 20 would be the correct answer. For example, a question could ask which VLAN is untagged on a switch where the administrator has changed the default native VLAN to 20.
Why candidates choose this
Candidates may choose VLAN 20 due to familiarity with VLAN configurations and assumptions that it could be a common choice for native VLANs, especially if they have encountered scenarios where VLAN 20 is used in practice.
✗The highest configured VLANWrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the default untagged VLAN on many Cisco switches is VLAN 1, not the highest configured VLAN. The highest configured VLAN can vary based on the network setup and does not have a default status in this context.
★ When this WOULD be the correct answer
In a different question asking which VLAN is used as the native VLAN when a switch is configured to use the highest VLAN number as the native VLAN, option D would be correct. For instance, if a switch has VLANs 1 through 50 configured and the question specifies that the highest VLAN is set as the native VLAN, then VLAN 50 would be the answer.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of VLAN configurations, thinking that the highest VLAN is always the default untagged VLAN, especially if they have encountered scenarios where custom configurations are used.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Key term
Native VLAN
A native VLAN is the default VLAN assigned to a trunk port that carries untagged traffic for backwards compatibility with devices that do not understand VLAN tagging.
Key term
802.1Q
802.1Q is the networking standard that allows multiple virtual LANs (VLANs) to share a single physical network link by tagging Ethernet frames with VLAN identification information.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.