Quick Answer
The answer is Layer 2, the Data Link layer. A switch operates at this layer because it forwards frames based on MAC addresses, which are hardware addresses assigned to network interfaces. The Data Link layer, defined by IEEE 802 standards, handles node-to-node data transfer and error detection, and switches build a MAC address table by learning source MAC addresses from incoming frames to make forwarding decisions. On the CompTIA Network+ N10-009 exam, this concept tests your understanding of how switches differ from hubs (Layer 1) and routers (Layer 3); a common trap is confusing a switch with a router because both forward traffic, but switches use MAC addresses while routers use IP addresses. To remember, think: “Switch sees the MAC, Layer 2 is its track.”
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.
A network switch that forwards frames based on MAC addresses operates at which layer of the OSI model?
Physical
Why wrong: Hubs and repeaters operate at Layer 1, not switches.
Data Link
Switches make forwarding decisions based on MAC addresses, which is a Layer 2 function.
Network
Why wrong: Routers operate at Layer 3, using IP addresses for forwarding.
Transport
Why wrong: Transport layer (Layer 4) deals with protocols like TCP and UDP, not MAC 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
Data Link
A network switch that forwards frames based on MAC addresses operates at Layer 2, the Data Link layer. This layer is responsible for node-to-node data transfer and error detection using MAC addresses, as defined by IEEE 802 standards. Switches build a MAC address table by learning source MAC addresses from incoming frames and use this table to make forwarding decisions.
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.
Physical
Why it's wrong here
Hubs and repeaters operate at Layer 1, not switches.
Data Link
Why this is correct
Switches make forwarding decisions based on MAC addresses, which is a Layer 2 function.
Related concept
Read the scenario before looking for a memorised answer.
Network
Why it's wrong here
Routers operate at Layer 3, using IP addresses for forwarding.
Transport
Common exam traps
Cisco often tests the misconception that switches operate at Layer 3 because they can be configured with IP addresses for management (e.g., SVI), but the core frame-forwarding function remains at Layer 2 using MAC addresses.
Detailed technical explanation
Under the hood, a switch's MAC address table is populated dynamically by examining the source MAC address of each incoming frame and associating it with the ingress port. When a frame arrives with a destination MAC not in the table, the switch floods the frame out all ports except the receiving port (unknown unicast flooding). In real-world scenarios, this behavior can cause unnecessary broadcast traffic in large networks, which is why features like VLANs and MAC address table limits are used to optimize performance.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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: Data Link — A network switch that forwards frames based on MAC addresses operates at Layer 2, the Data Link layer. This layer is responsible for node-to-node data transfer and error detection using MAC addresses, as defined by IEEE 802 standards. Switches build a MAC address table by learning source MAC addresses from incoming frames and use this table to make forwarding decisions.
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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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. At which layer of the OSI model does a switch that uses MAC addresses to forward frames operate?
easyWhy B: 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.
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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