The answer is ARP, the Address Resolution Protocol, which is the correct choice because it performs the essential function of resolving a known IP address to its corresponding MAC address on a local network. When a host needs to communicate with another device on the same subnet, it broadcasts an ARP request containing the target IP; the device that owns that IP responds with its MAC address, which is then cached for efficiency. On the CompTIA Network+ N10-009 exam, this concept tests your understanding of Layer 2 and Layer 3 interaction, often appearing in questions about frame delivery or network troubleshooting. A common trap is confusing ARP with DNS, which resolves names to IPs, not IPs to MACs. Remember the memory tip: ARP is for the "local hop" — it maps IP to MAC so frames can travel across the switch, not across routers.
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Which protocol is used to resolve a known IP address to a corresponding MAC address on a local network?
ARP (Address Resolution Protocol) maps IPv4 addresses to MAC addresses. It is essential for local network communication.
B
DNS
Why wrong: DNS (Domain Name System) resolves domain names to IP addresses, not IP addresses to MAC addresses.
C
DHCP
Why wrong: DHCP (Dynamic Host Configuration Protocol) assigns IP addresses and other configuration parameters to hosts, but does not resolve IP addresses to MAC addresses.
D
ICMP
Why wrong: ICMP (Internet Control Message Protocol) is used for error reporting and diagnostic functions like ping, not for address resolution.
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 used to resolve a known IP address to its corresponding MAC address on a local network. When a host needs to send a frame to another host on the same subnet, it broadcasts an ARP request containing the target IP; the host with that IP responds with its MAC address, which is then cached for future use.
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.
✓
ARP
Why this is correct
ARP (Address Resolution Protocol) maps IPv4 addresses to MAC addresses. It is essential for local network communication.
Related concept
Read the scenario before looking for a memorised answer.
✗
DNS
Why it's wrong here
DNS (Domain Name System) resolves domain names to IP addresses, not IP addresses to MAC addresses.
✗
DHCP
Why it's wrong here
DHCP (Dynamic Host Configuration Protocol) assigns IP addresses and other configuration parameters to hosts, but does not resolve IP addresses to MAC addresses.
✗
ICMP
Why it's wrong here
ICMP (Internet Control Message Protocol) is used for error reporting and diagnostic functions like ping, not for address resolution.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing ARP with DNS, as both involve 'resolution,' but DNS resolves names to IPs (Layer 3) while ARP resolves IPs to MACs (Layer 2), and candidates often forget ARP operates only within a local broadcast domain.
Detailed technical explanation
How to think about this question
ARP operates at Layer 2 (Data Link) and Layer 3 (Network) boundary, using broadcast frames (FF:FF:FF:FF:FF:FF) for requests and unicast for replies. The ARP cache on each host stores mappings with a timeout (typically 2–4 minutes for dynamic entries), and gratuitous ARP is used to detect IP conflicts or update switches' MAC tables after a NIC replacement.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
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: ARP — ARP (Address Resolution Protocol) is used to resolve a known IP address to its corresponding MAC address on a local network. When a host needs to send a frame to another host on the same subnet, it broadcasts an ARP request containing the target IP; the host with that IP responds with its MAC address, which is then cached for future use.
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.
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Question Discussion
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