N10-009 Networking Concepts Practice Question
A junior network technician asks which device operates at Layer 2 of the OSI model and uses MAC addresses to forward frames. Which device is the technician describing?
⚠ Common exam trap
The N10-009 exam often tests the distinction between Layer 2 and Layer 3 devices by asking about forwarding decisions based on MAC vs. IP addresses, and the trap here is that candidates may confuse a switch with a router because both can connect multiple devices, but only the switch operates purely at Layer 2 using MAC addresses.
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
✓
Switch
A switch operates at Layer 2 (Data Link layer) of the OSI model and uses MAC addresses to make forwarding decisions. It builds a MAC address table by learning source MAC addresses from incoming frames and then forwards frames only to the specific port associated with the destination MAC address, reducing collision domains and improving network efficiency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Hub
Why it's wrong here
Hubs are basic networking devices that operate solely at Layer 1 (Physical Layer) of the OSI model. They function as multi-port repeaters, simply receiving an electrical signal on one port and regenerating it to all other connected ports without any intelligence or awareness of data frames or MAC addresses. This creates a single large collision domain, meaning all devices connected to a hub share the same bandwidth and are susceptible to collisions, making them inefficient for modern networks.
When this WOULD be correct
A question asking 'Which device operates at Layer 1 of the OSI model and regenerates signals?' would have Hub as the correct answer.
- ✓
Switch
Why this is correct
Switches operate primarily at Layer 2 (Data Link Layer) of the OSI model. They intelligently forward data frames based on the destination Media Access Control (MAC) address found in the frame header. By learning MAC addresses and storing them in a MAC address table, switches create dedicated collision domains for each port, significantly improving network efficiency compared to hubs. This targeted forwarding ensures data only reaches the intended recipient, reducing unnecessary network traffic.
- ✗
Router
Why it's wrong here
Routers function at Layer 3 (Network Layer) of the OSI model, using Internet Protocol (IP) addresses to forward packets between different network segments or subnets. Their primary role is to connect disparate networks and intelligently determine the optimal path for data packets to reach their destination across various networks. Unlike switches, routers break up broadcast domains and do not forward traffic based on MAC addresses across different subnets.
When this WOULD be correct
A question asking 'Which device operates at Layer 3 of the OSI model and uses IP addresses to route packets between networks?' would make Router the correct answer.
- ✗
Firewall
Why it's wrong here
Firewalls are security devices designed to control network traffic based on a set of rules, primarily operating at Layer 3 (Network Layer) and Layer 4 (Transport Layer) to inspect IP addresses and port numbers. While some advanced firewalls, known as Layer 2 firewalls or transparent firewalls, can operate at the Data Link Layer, their core function is not simply forwarding frames based on MAC addresses. Instead, they focus on stateful packet inspection and application-layer filtering to enforce security policies across network boundaries.
When this WOULD be correct
A question asking 'Which device is used to filter traffic based on IP addresses and ports to protect a network from unauthorized access?' would have firewall as 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.
✓SwitchCorrect answer▾
Why this is correct
Switches operate primarily at Layer 2 (Data Link Layer) of the OSI model. They intelligently forward data frames based on the destination Media Access Control (MAC) address found in the frame header. By learning MAC addresses and storing them in a MAC address table, switches create dedicated collision domains for each port, significantly improving network efficiency compared to hubs. This targeted forwarding ensures data only reaches the intended recipient, reducing unnecessary network traffic.
✗HubWrong answer — click to see why▾
Why this is wrong here
Hubs operate at Layer 1 (Physical layer) and simply repeat electrical signals to all ports; they do not use MAC addresses to forward frames.
★ When this WOULD be the correct answer
A question asking 'Which device operates at Layer 1 of the OSI model and regenerates signals?' would have Hub as the correct answer.
Why candidates choose this
Candidates may confuse hubs with switches because both have multiple ports and are used in LANs, but hubs lack the intelligence to process MAC addresses.
✗RouterWrong answer — click to see why▾
Why this is wrong here
Routers operate at Layer 3 (Network layer) and use IP addresses to forward packets, not MAC addresses to forward frames.
★ When this WOULD be the correct answer
A question asking 'Which device operates at Layer 3 of the OSI model and uses IP addresses to route packets between networks?' would make Router the correct answer.
Why candidates choose this
Candidates may confuse the functions of switches and routers, especially if they recall that routers forward traffic but forget the layer distinction.
✗FirewallWrong answer — click to see why▾
Why this is wrong here
A firewall operates at Layers 3 and 4 (and sometimes higher) of the OSI model, using IP addresses and ports to filter traffic, not MAC addresses to forward frames.
★ When this WOULD be the correct answer
A question asking 'Which device is used to filter traffic based on IP addresses and ports to protect a network from unauthorized access?' would have firewall as the correct answer.
Why candidates choose this
Candidates may confuse firewalls with switches because both are network devices that filter traffic, but they operate at different layers and use different addressing.
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?”
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 |
Go deeper
Related to this question
Learn chapter
Network Virtualization and VXLAN
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.
Key term
MAC address
A MAC address is a unique hardware identifier assigned to a network interface card that allows devices to communicate on a local network.
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.