Quick Answer
The answer is the Address Resolution Protocol, or ARP. ARP is the correct choice because it is the dedicated mechanism for resolving a known Layer 3 IP address to an unknown Layer 2 MAC address on a local network; when a host needs to communicate, it broadcasts an ARP request containing the target IP, and the device with that IP replies with its MAC address, a process defined in RFC 826. On the CompTIA Network+ N10-009 exam, this question tests your understanding of how hosts map logical addresses to physical hardware addresses within the same broadcast domain, and a common trap is confusing ARP with DNS—remember that DNS resolves names to IPs, while ARP resolves IPs to MACs. For a quick memory tip, think of ARP as the “address finder” that bridges Layer 3 and Layer 2, and recall the mnemonic “ARP Answers Real Packets” to reinforce its role in local network delivery.
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 technician is explaining the process of resolving Layer 2 addresses to Layer 3 addresses on a local network. Which protocol is used by a host to determine the MAC address of another host given its IP address?
DNS
Why wrong: DNS resolves domain names to IP addresses, not MAC addresses.
ARP
Address Resolution Protocol (ARP) maps an IPv4 address to a MAC address on the same local network.
DHCP
Why wrong: DHCP assigns IP addresses and other configuration, but does not resolve IP to MAC addresses.
ICMP
Why wrong: ICMP is used for error reporting and diagnostic functions like ping, not for address resolution.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ARP
ARP (Address Resolution Protocol) is the correct answer because it is specifically designed to resolve a known Layer 3 (IP) address to an unknown Layer 2 (MAC) address on a local network. When a host needs to send a frame to another host, it first checks its ARP cache; if no entry exists, it broadcasts an ARP request containing the target IP, and the host with that IP responds with its MAC address. This process is defined in RFC 826 and operates at the data link layer, enabling direct communication within the same broadcast domain.
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.
DNS
Why it's wrong here
DNS resolves domain names to IP addresses, not MAC addresses.
ARP
Why this is correct
Address Resolution Protocol (ARP) maps an IPv4 address to a MAC address on the same local network.
Related concept
Read the scenario before looking for a memorised answer.
DHCP
Why it's wrong here
DHCP assigns IP addresses and other configuration, but does not resolve IP to MAC addresses.
ICMP
Why it's wrong here
ICMP is used for error reporting and diagnostic functions like ping, not for address resolution.
Common exam traps
The trap here is that candidates often confuse ARP with DNS because both involve 'resolution,' but DNS resolves names to IPs (Layer 3) while ARP resolves IPs to MACs (Layer 2), and Cisco tests this distinction by including DNS as a distractor in Layer 2 addressing questions.
Detailed technical explanation
Under the hood, ARP uses a two-message exchange: the broadcast request (opcode 1) and the unicast reply (opcode 2), with the target MAC address initially set to 00:00:00:00:00:00 in the request. A subtle behavior is that ARP is a stateless protocol, meaning a host can send a gratuitous ARP to announce its own IP-to-MAC mapping or detect IP conflicts. In real-world scenarios, ARP spoofing attacks exploit this by sending forged ARP replies to redirect traffic, which is why dynamic ARP inspection (DAI) is used in secure networks.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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: ARP — ARP (Address Resolution Protocol) is the correct answer because it is specifically designed to resolve a known Layer 3 (IP) address to an unknown Layer 2 (MAC) address on a local network. When a host needs to send a frame to another host, it first checks its ARP cache; if no entry exists, it broadcasts an ARP request containing the target IP, and the host with that IP responds with its MAC address. This process is defined in RFC 826 and operates at the data link layer, enabling direct communication within the same broadcast domain.
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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