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200-901 Practice Question: Is configuring a new switch and needs to ensure…
A network engineer is configuring a new switch and needs to ensure that frames from VLAN 10 and VLAN 20 are isolated on the same trunk link to another switch. Which IEEE standard should be configured on the trunk interfaces?
⚠ Common exam trap
Cisco often tests the distinction between 802.1Q (VLAN tagging) and 802.1X (authentication), so the trap here is confusing a trunking protocol with a security protocol, leading candidates to pick 802.1X when the question is about VLAN isolation on a trunk.
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
✓
802.1Q
C is correct because 802.1Q is the IEEE standard that defines VLAN tagging, allowing multiple VLANs (such as VLAN 10 and VLAN 20) to be carried over a single trunk link while maintaining isolation between them. By inserting a 4-byte VLAN tag into the Ethernet frame, 802.1Q enables the receiving switch to identify which VLAN a frame belongs to, ensuring traffic from different VLANs remains separate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
802.3
Why it's wrong here
802.3 is the Ethernet standard, not for VLAN trunking.
- ✗
802.11
Why it's wrong here
802.11 is for wireless LANs, not trunking.
- ✓
802.1Q
Why this is correct
802.1Q is the IEEE standard for VLAN tagging on trunk links.
- ✗
802.1X
Why it's wrong here
802.1X is for network access control, not trunking.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.