N10-009 Networking Concepts Practice Question
Which of the following uniquely identifies a hardware network interface on a device?
⚠ Common exam trap
It's easy for candidates to confuse the MAC address with the IP address, thinking the IP address is the hardware identifier, but CompTIA tests that the MAC address is the only Layer 2 permanent identifier, while IP addresses are logical and can be reassigned via DHCP or static configuration.
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
✓
MAC address
A MAC (Media Access Control) address is a hardware-embedded, globally unique identifier assigned to a network interface controller (NIC) by the manufacturer. It operates at Layer 2 (Data Link Layer) of the OSI model and is used for local network communication, ensuring that no two devices on the same broadcast domain have the same MAC address.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
MAC address
Why this is correct
A MAC address is a 48-bit hardware identifier burned into the network interface controller, uniquely identifying that interface within its broadcast domain. IP addresses are logical and reassignable, so they do not uniquely identify the physical interface.
- ✗
IP address
Why it's wrong here
An IP address is a logical Layer 3 identifier assigned by configuration or DHCP, and it changes when a host moves networks or leases expire, so it does not uniquely identify the hardware interface. It is tempting because IP addresses are commonly used to address and locate hosts, and for routing traffic to a specific device it would be the correct choice.
When this WOULD be correct
When a question asks 'Which of the following identifies a device on a network for routing purposes?' or 'Which address is used for communication between networks?', IP address would be correct.
- ✗
Subnet mask
Why it's wrong here
A subnet mask defines which portion of an IP address represents the network and which represents the host; it is shared across every device in the subnet and identifies no individual interface. It is tempting because it is essential for determining local versus remote destinations, and for calculating subnet boundaries it would be the correct choice.
When this WOULD be correct
In a question asking 'Which value determines the network portion of an IP address?', the subnet mask would be the correct answer.
- ✗
Default gateway
Why it's wrong here
A default gateway is the router address a host uses for off-subnet traffic; many hosts on the same subnet share one gateway address, so it identifies no individual interface. It is tempting because it is a required configuration for reaching external networks, and for troubleshooting failed off-subnet connectivity it would be the correct choice.
When this WOULD be correct
In a question asking 'Which IP address should be configured as the next-hop for traffic destined to the internet?', the default gateway would be 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.
✓MAC addressCorrect answer▾
Why this is correct
A MAC address is a 48-bit hardware identifier burned into the network interface controller, uniquely identifying that interface within its broadcast domain. IP addresses are logical and reassignable, so they do not uniquely identify the physical interface.
✗IP addressWrong answer — click to see why▾
Why this is wrong here
An IP address identifies a device on a network layer, not the hardware interface itself, and can change dynamically or be reassigned.
★ When this WOULD be the correct answer
When a question asks 'Which of the following identifies a device on a network for routing purposes?' or 'Which address is used for communication between networks?', IP address would be correct.
Why candidates choose this
Candidates often confuse network-layer identification (IP) with hardware-layer identification (MAC), especially when thinking about 'identifying a device' on a network.
✗Subnet maskWrong answer — click to see why▾
Why this is wrong here
A subnet mask defines the network and host portions of an IP address, but it does not uniquely identify a hardware network interface; it is a logical parameter used for routing.
★ When this WOULD be the correct answer
In a question asking 'Which value determines the network portion of an IP address?', the subnet mask would be the correct answer.
Why candidates choose this
Candidates may confuse subnet masks with MAC addresses because both are associated with network configuration, or they might think the subnet mask is tied to the interface in some unique way.
✗Default gatewayWrong answer — click to see why▾
Why this is wrong here
A default gateway is a router's IP address used for traffic outside the local subnet, not a unique identifier for a hardware network interface.
★ When this WOULD be the correct answer
In a question asking 'Which IP address should be configured as the next-hop for traffic destined to the internet?', the default gateway would be the correct answer.
Why candidates choose this
Candidates may confuse the default gateway as a network identifier because it is a critical network setting often associated with a specific interface, but it does not uniquely identify the interface itself.
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
TCP/IP Model and Protocol Suite
Key term
OSI model
The OSI model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers, from physical hardware to application software.
Key term
Least privilege
Least privilege is a security principle that means giving users, systems, or programs only the minimum permissions they need to do their job and nothing more.
About these practice questions
This N10-009 question is part of Courseiva's 472-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.