N10-009 Network Implementation Practice Question
A network administrator is configuring a new switch to carry traffic for multiple VLANs on a single link to a router. Which IEEE standard is used for VLAN tagging on Ethernet trunks?
⚠ Common exam trap
The N10-009 exam often tests the distinction between 802.1Q (tagging) and 802.1D (STP), leading candidates to confuse VLAN trunking with loop prevention protocols.
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
802.1Q is the IEEE standard that defines VLAN tagging on Ethernet trunks, inserting a 4-byte tag into the Ethernet frame to identify VLAN membership. This allows multiple VLANs to traverse a single link between a switch and a router, enabling inter-VLAN routing without separate physical interfaces.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
802.3af
Why it's wrong here
802.3af defines Power over Ethernet (PoE) delivery, not frame tagging; it cannot encapsulate VLAN membership information within Ethernet frames. It is tempting because 802.3af is a common IEEE standard for switch-to-device connections, but the scenario requires 802.1Q to insert a VLAN identifier into the trunk link header, which 802.3af lacks entirely.
When this WOULD be correct
A question asking which standard provides power to devices like IP cameras or wireless access points over Ethernet cabling would have 802.3af as the correct answer.
- ✗
802.1D
Why it's wrong here
IEEE 802.1D defines the Spanning Tree Protocol (STP), a crucial network protocol designed to prevent Layer 2 switching loops in redundant network topologies. STP achieves this by logically blocking redundant paths, ensuring only a single active path exists between any two network devices. While essential for network stability and preventing broadcast storms, 802.1D operates independently of VLAN identification and does not provide any mechanism for tagging or encapsulating VLAN membership information within Ethernet frames.
When this WOULD be correct
A question asking 'Which IEEE standard defines the Spanning Tree Protocol for loop prevention in Ethernet networks?' would make 802.1D the correct answer.
- ✓
802.1Q
Why this is correct
IEEE 802.1Q is the industry standard for Virtual Local Area Network (VLAN) tagging on Ethernet networks. It inserts a 4-byte tag into the Ethernet frame header, specifically between the Source Address and Type/Length fields, to carry VLAN identification (VID) information. This tagging allows a single physical link, known as a trunk port, to transport traffic for multiple VLANs, enabling switches to correctly forward frames to their intended VLAN segments. Without 802.1Q, a switch port can typically only belong to a single VLAN.
- ✗
802.11ac
Why it's wrong here
IEEE 802.11ac is a wireless networking standard that defines specifications for very high throughput (VHT) Wireless Local Area Networks (WLANs) operating primarily in the 5 GHz frequency band. It focuses on enhancing Wi-Fi speeds and efficiency for devices connecting wirelessly to an access point. This standard is entirely unrelated to the physical layer or data link layer protocols used for tagging Ethernet frames on wired switches to carry VLAN traffic.
When this WOULD be correct
When asked which IEEE standard supports high-throughput wireless LANs in the 5 GHz band with multi-user MIMO, 802.11ac would be the correct 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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓802.1QCorrect answer▾
Why this is correct
IEEE 802.1Q is the industry standard for Virtual Local Area Network (VLAN) tagging on Ethernet networks. It inserts a 4-byte tag into the Ethernet frame header, specifically between the Source Address and Type/Length fields, to carry VLAN identification (VID) information. This tagging allows a single physical link, known as a trunk port, to transport traffic for multiple VLANs, enabling switches to correctly forward frames to their intended VLAN segments. Without 802.1Q, a switch port can typically only belong to a single VLAN.
✗802.3afWrong answer — click to see why▾
Why this is wrong here
802.3af is the IEEE standard for Power over Ethernet (PoE), not for VLAN tagging on Ethernet trunks.
★ When this WOULD be the correct answer
A question asking which standard provides power to devices like IP cameras or wireless access points over Ethernet cabling would have 802.3af as the correct answer.
Why candidates choose this
Candidates may confuse the 802.3 series with 802.1 standards, or mistakenly think that PoE is related to trunking because both are common switch features.
✗802.1DWrong answer — click to see why▾
Why this is wrong here
802.1D is the IEEE standard for Spanning Tree Protocol (STP), not for VLAN tagging on Ethernet trunks. VLAN tagging is defined by 802.1Q.
★ When this WOULD be the correct answer
A question asking 'Which IEEE standard defines the Spanning Tree Protocol for loop prevention in Ethernet networks?' would make 802.1D the correct answer.
Why candidates choose this
Candidates may confuse 802.1D with 802.1Q due to similar numbering, or mistakenly think that trunking involves spanning tree concepts.
✗802.11acWrong answer — click to see why▾
Why this is wrong here
802.11ac is a wireless networking standard for Wi-Fi, not used for VLAN tagging on Ethernet trunks.
★ When this WOULD be the correct answer
When asked which IEEE standard supports high-throughput wireless LANs in the 5 GHz band with multi-user MIMO, 802.11ac would be the correct answer.
Why candidates choose this
Candidates may confuse the 802.11 series (wireless) with 802.1 series (networking/bridging) due to similar numbering, or mistakenly think VLAN tagging applies to wireless links.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Go deeper
Related to this question
Learn chapter
Ethernet Switching and VLANs
Key term
Switch Virtual Interface
A logical interface on a network switch that allows it to be managed and communicate with other devices using IP addresses.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.