- A
DNS
Why wrong: DNS resolves domain names to IP addresses, not MAC addresses.
- B
ARP
Address Resolution Protocol (ARP) maps an IPv4 address to a MAC address on the same local network.
- C
DHCP
Why wrong: DHCP assigns IP addresses and other configuration, but does not resolve IP to MAC addresses.
- D
ICMP
Why wrong: ICMP is used for error reporting and diagnostic functions like ping, not for address resolution.
Question 22 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 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?
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
✓
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DNS
- ✓
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.
When this WOULD be correct
A question asking which protocol is used to test reachability between hosts or to report network errors (e.g., 'Which protocol does ping use?') would have ICMP 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.
✓ARPCorrect answer▾
Why this is correct
Address Resolution Protocol (ARP) maps an IPv4 address to a MAC address on the same local network.
✗DNSWrong answer — click to see why▾
Why this is wrong here
DNS resolves domain names to IP addresses, not MAC addresses. The question asks for the protocol that maps IP addresses (Layer 3) to MAC addresses (Layer 2), which is ARP.
★ When this WOULD be the correct answer
DNS would be correct in a question like: 'Which protocol is used to resolve a fully qualified domain name (FQDN) to an IP address?'
Why candidates choose this
Candidates may confuse 'address resolution' with DNS's name resolution, or think that DNS handles all types of address mapping on a network.
✗DHCPWrong answer — click to see why▾
Why this is wrong here
DHCP is used for dynamically assigning IP addresses and other network configuration parameters to hosts, not for resolving Layer 2 MAC addresses from Layer 3 IP addresses.
★ When this WOULD be the correct answer
A question asking which protocol automatically assigns IP addresses, subnet masks, default gateways, and DNS server addresses to hosts on a network would have DHCP as the correct answer.
Why candidates choose this
Candidates may confuse DHCP with ARP because both operate at the network layer and involve address assignment or resolution, leading them to think DHCP handles MAC-to-IP mapping.
✗ICMPWrong answer — click to see why▾
Why this is wrong here
ICMP is used for error reporting and diagnostics (e.g., ping), not for resolving Layer 2 addresses from Layer 3 addresses.
★ When this WOULD be the correct answer
A question asking which protocol is used to test reachability between hosts or to report network errors (e.g., 'Which protocol does ping use?') would have ICMP as the correct answer.
Why candidates choose this
Candidates may confuse ICMP's role in network troubleshooting with address resolution, or think that ICMP's use in ping involves MAC address discovery.
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 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
How to think about this question
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.
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.
Visual reference
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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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: 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.
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
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