N10-009 Network Implementation Practice Question
A network administrator needs to connect two switches to allow multiple VLANs to traverse the link. Which protocol should be used to tag frames with VLAN information?
⚠ Common exam trap
Many exam-takers confuse VTP (a management protocol) with the actual tagging protocol, assuming VTP handles frame tagging because of the word 'trunking' in its name.
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 for VLAN tagging, which inserts a 4-byte tag into the Ethernet frame header to identify the VLAN membership of the frame. This allows multiple VLANs to traverse a single trunk link between switches, enabling inter-switch VLAN communication without requiring separate physical links per VLAN.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
STP (Spanning Tree Protocol)
Why it's wrong here
Spanning Tree Protocol (STP) is designed to prevent network loops in redundant Layer 2 topologies by selectively blocking redundant paths, ensuring a single active path between any two network devices. While crucial for network stability and preventing broadcast storms, STP operates independently of VLAN identification and does not add any tagging information to Ethernet frames. It solely focuses on path redundancy and loop avoidance, not on distinguishing traffic from different VLANs.
When this WOULD be correct
A question asking which protocol prevents bridging loops in a redundant switched network, where the correct answer is STP (802.1D).
- ✓
802.1Q
Why this is correct
IEEE 802.1Q is the industry standard for VLAN tagging, which is essential for allowing multiple Virtual Local Area Networks (VLANs) to share a single physical link between network devices like switches. It inserts a 4-byte tag into the Ethernet frame header, containing a 12-bit VLAN ID (VID) that identifies the specific VLAN the frame belongs to. This tagging mechanism ensures that frames from different VLANs remain logically separate while traversing a shared trunk port, enabling efficient network segmentation and traffic isolation.
- ✗
VTP (VLAN Trunking Protocol)
Why it's wrong here
VLAN Trunking Protocol (VTP) is a Cisco-proprietary protocol used to synchronize VLAN configuration information, such as VLAN names and IDs, across multiple switches within the same VTP domain. Its primary role is to simplify VLAN management by propagating changes from a VTP server to client switches, reducing administrative overhead. However, VTP itself does not tag individual Ethernet frames with VLAN identifiers; it relies on an underlying trunking protocol like 802.1Q or ISL to actually encapsulate and transport VLAN-tagged traffic across the trunk links.
When this WOULD be correct
A network administrator needs to automatically propagate VLAN configuration changes from one switch to others in the same VTP domain. VTP would be the correct protocol to use.
- ✗
LACP (Link Aggregation Control Protocol)
Why it's wrong here
Link Aggregation Control Protocol (LACP) is used to bundle multiple physical Ethernet links into a single logical link, known as a link aggregation group (LAG) or EtherChannel. This aggregation increases bandwidth and provides redundancy in case one of the physical links fails. However, LACP's function is solely to manage the bundling of links and distribute traffic across them; it does not perform any VLAN tagging or provide a mechanism for identifying which VLAN a particular frame belongs to.
When this WOULD be correct
A network administrator needs to increase bandwidth and provide redundancy between two switches by combining multiple physical links into a single logical link. Which protocol should be used?
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 VLAN tagging, which is essential for allowing multiple Virtual Local Area Networks (VLANs) to share a single physical link between network devices like switches. It inserts a 4-byte tag into the Ethernet frame header, containing a 12-bit VLAN ID (VID) that identifies the specific VLAN the frame belongs to. This tagging mechanism ensures that frames from different VLANs remain logically separate while traversing a shared trunk port, enabling efficient network segmentation and traffic isolation.
✗STP (Spanning Tree Protocol)Wrong answer — click to see why▾
Why this is wrong here
STP prevents loops in a network but does not tag frames with VLAN information; it operates at Layer 2 to block redundant paths, not to identify VLAN membership.
★ When this WOULD be the correct answer
A question asking which protocol prevents bridging loops in a redundant switched network, where the correct answer is STP (802.1D).
Why candidates choose this
Candidates may confuse STP with trunking protocols because both are associated with switches, but STP's role in loop prevention is unrelated to VLAN tagging.
✗VTP (VLAN Trunking Protocol)Wrong answer — click to see why▾
Why this is wrong here
VTP is used to synchronize VLAN information across switches, not to tag frames with VLAN information. The protocol for tagging frames is 802.1Q.
★ When this WOULD be the correct answer
A network administrator needs to automatically propagate VLAN configuration changes from one switch to others in the same VTP domain. VTP would be the correct protocol to use.
Why candidates choose this
Candidates may confuse VTP with VLAN trunking because of the word 'trunking' in its name, but VTP manages VLAN databases, not frame tagging.
✗LACP (Link Aggregation Control Protocol)Wrong answer — click to see why▾
Why this is wrong here
LACP is used for link aggregation (combining multiple physical links into one logical link) to increase bandwidth and provide redundancy, not for tagging frames with VLAN information.
★ When this WOULD be the correct answer
A network administrator needs to increase bandwidth and provide redundancy between two switches by combining multiple physical links into a single logical link. Which protocol should be used?
Why candidates choose this
Candidates may confuse LACP with trunking protocols because both are associated with switch-to-switch links, but LACP handles aggregation, not VLAN tagging.
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
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Related to this question
Learn chapter
Ethernet Switching and VLANs
Key term
VLAN
A VLAN (Virtual Local Area Network) is a logical grouping of network devices that behave as if they are on the same physical network segment, regardless of their actual physical location.
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.
About these practice questions
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JA
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.