This N10-009 practice question tests your understanding of networking concepts. 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.
At which layer of the OSI model does a switch that uses MAC addresses to forward frames operate?
Layer 1
Why wrong: Layer 1 deals with physical media and signals, not MAC addresses.
Layer 2
Layer 2 (Data Link layer) uses MAC addresses to switch frames within a network segment.
Layer 3
Why wrong: Layer 3 (Network layer) uses IP addresses for routing, not MAC addresses for switching.
Layer 4
Why wrong: Layer 4 (Transport layer) handles end-to-end communication and flow control, not frame forwarding.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Layer 2
A switch that uses MAC addresses to forward frames operates at Layer 2 (Data Link layer) of the OSI model. Layer 2 is responsible for node-to-node data transfer and error detection, using MAC addresses as the addressing scheme. The switch builds a MAC address table by learning source MAC addresses from incoming frames and then forwards frames based on the destination MAC address, making forwarding decisions at this layer.
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.
Layer 1
Why it's wrong here
Layer 1 deals with physical media and signals, not MAC addresses.
Layer 2
Why this is correct
Layer 2 (Data Link layer) uses MAC addresses to switch frames within a network segment.
Related concept
Read the scenario before looking for a memorised answer.
Layer 3
Why it's wrong here
Layer 3 (Network layer) uses IP addresses for routing, not MAC addresses for switching.
Layer 4
Why it's wrong here
Layer 4 (Transport layer) handles end-to-end communication and flow control, not frame forwarding.
Common exam traps
The trap here is that candidates often confuse a switch's MAC address-based forwarding with a router's IP-based forwarding, mistakenly selecting Layer 3, or they think of a hub's operation at Layer 1 and incorrectly apply that to a switch.
Detailed technical explanation
Under the hood, a Layer 2 switch maintains a Content Addressable Memory (CAM) table that maps MAC addresses to specific switch ports. When a frame arrives, the switch performs a lookup in the CAM table; if the destination MAC is found, the frame is forwarded only to the associated port (unicast), otherwise it floods the frame to all ports except the ingress port. In real-world scenarios, this behavior is critical for VLAN segmentation, where switches use 802.1Q tags to isolate traffic at Layer 2, and STP (Spanning Tree Protocol) prevents loops by blocking redundant paths.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
The correct answer is: Layer 2 — A switch that uses MAC addresses to forward frames operates at Layer 2 (Data Link layer) of the OSI model. Layer 2 is responsible for node-to-node data transfer and error detection, using MAC addresses as the addressing scheme. The switch builds a MAC address table by learning source MAC addresses from incoming frames and then forwards frames based on the destination MAC address, making forwarding decisions at this layer.
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 11, 2026
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.
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