- A
Physical
Why wrong: Hubs and repeaters operate at Layer 1, not switches.
- B
Data Link
Switches make forwarding decisions based on MAC addresses, which is a Layer 2 function.
- C
Network
Why wrong: Routers operate at Layer 3, using IP addresses for forwarding.
- D
Transport
Why wrong: Transport layer (Layer 4) deals with protocols like TCP and UDP, not MAC forwarding.
Question 448 of 520
N10-009 Networking Concepts Practice Question
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?
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
✓
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
Option-by-option breakdown
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.
When this WOULD be correct
A question asking 'Which OSI layer defines electrical signals, cabling, and bit transmission?' would have Physical as the correct answer. Also, if the question were 'A repeater operates at which layer?', Physical would be correct.
- ✓
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.
When this WOULD be correct
A question asking 'Which OSI layer routes packets based on IP addresses?' or 'At which layer does a router operate?' would have Network as the correct answer.
- ✗
Transport
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.
✓Data LinkCorrect answer▾
Why this is correct
Switches make forwarding decisions based on MAC addresses, which is a Layer 2 function.
✗PhysicalWrong answer — click to see why▾
Why this is wrong here
The Physical layer (Layer 1) handles raw bit transmission over a physical medium, not MAC address-based frame forwarding. A switch that forwards frames using MAC addresses operates at the Data Link layer (Layer 2).
★ When this WOULD be the correct answer
A question asking 'Which OSI layer defines electrical signals, cabling, and bit transmission?' would have Physical as the correct answer. Also, if the question were 'A repeater operates at which layer?', Physical would be correct.
Why candidates choose this
Candidates may confuse the switch's physical ports and cabling with the Physical layer, not realizing that the switching logic (MAC address table) is a Data Link layer function.
✗NetworkWrong answer — click to see why▾
Why this is wrong here
The Network layer (Layer 3) uses logical addressing (e.g., IP addresses) for routing packets between networks, not MAC addresses for forwarding frames within a single network.
★ When this WOULD be the correct answer
A question asking 'Which OSI layer routes packets based on IP addresses?' or 'At which layer does a router operate?' would have Network as the correct answer.
Why candidates choose this
Candidates may confuse MAC address forwarding with IP routing, or think that 'network' broadly refers to all networking functions, leading them to select the Network layer.
✗TransportWrong answer — click to see why▾
Why this is wrong here
The Transport layer (Layer 4) handles end-to-end communication, segmentation, and flow control, not MAC address-based frame forwarding, which is a Layer 2 function.
★ When this WOULD be the correct answer
A question asking which OSI layer provides reliable data transfer between hosts, such as TCP's connection-oriented service, would have Transport as the correct answer.
Why candidates choose this
Candidates may confuse the switch's forwarding decision with higher-layer protocols, or think that MAC addresses are part of the Transport layer because they are associated with network interfaces.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The N10-009 exam 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
How to think about this question
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.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Networking Concepts — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this N10-009 question test?
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
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.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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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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