CCNA Network Services and Security Practice Question
Which service would a client most directly rely on to convert `server.example.com` into an IP address?
⚠ Common exam trap
A frequent exam trap is mistaking ARP for DNS because both involve address resolution. However, ARP only resolves IPv4 addresses to MAC addresses within the same local network segment and does not translate hostnames to IP addresses. Candidates might also confuse NTP or CDP as name resolution services, but NTP is for time synchronization, and CDP discovers directly connected Cisco devices. Misunderstanding these roles leads to selecting incorrect answers, especially since the question specifically asks about converting a hostname to an IP address, which only DNS performs.
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
✓
DNS
The client relies on DNS for name resolution. In plain language, DNS is the service that lets devices and users use readable names instead of memorizing numeric IP addresses. When the client needs to reach `server.example.com`, DNS helps translate that hostname into the IP-related information needed for actual communication. This is different from DHCP, which supplies address configuration, and from NTP, which synchronizes time. It is also different from ARP, which resolves local IPv4 addresses to MAC addresses. The correct answer is the one associated specifically with hostname resolution.
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
Why this is correct
The Domain Name System is the service that directly performs hostname-to-IP address resolution. When a client types a URL like www.cisco.com, it sends a DNS query to a resolver, which returns the corresponding IPv4 or IPv6 address. This is the fundamental name resolution service on which applications rely before establishing TCP connections. Without DNS, users would need to memorize numeric IP addresses.
- ✗
ARP
Why it's wrong here
Address Resolution Protocol operates at Layer 2 (data link) and maps a known IPv4 address to a MAC address on a local subnet. It is used after a host already knows the destination IP, typically obtained via DNS, and needs to encapsulate frames. ARP never resolves hostnames; it resolves IP-to-MAC mappings within a broadcast domain. Thus, it cannot convert a hostname into an IP address.
When this WOULD be correct
If the question asked about determining the MAC address of a device given its IP address within a local network, ARP would be the correct answer. For example, 'Which protocol is used to resolve an IP address to a MAC address on a local network?' would make ARP the right choice.
- ✗
NTP
Why it's wrong here
Network Time Protocol is used to synchronize the clocks of network devices and hosts to a time source such as an atomic clock or GPS. It ensures that timestamping for logs, authentication, and scheduling is consistent across devices. NTP has no role in name resolution; it operates on the application layer to distribute time, not addressing information. A client would never query NTP to convert a hostname.
When this WOULD be correct
If the exam question asked which service is responsible for synchronizing the time on a networked device, then NTP would be the correct answer. For example, a question could state, 'Which protocol ensures accurate timekeeping across devices in a network?'
- ✗
CDP
Why it's wrong here
Cisco Discovery Protocol is a proprietary Layer 2 protocol that allows Cisco devices to share information about directly connected neighbors, such as device type, IP address, and platform. CDP is used for network discovery and mapping, not for resolving hostnames requested by a client. A client application does not rely on CDP to translate a name into an IP; CDP advertisements are sent to a multicast address and are not consulted by typical host processes. Therefore, CDP is unrelated to hostname resolution.
When this WOULD be correct
In a question asking about the identification of neighboring Cisco devices on a network, such as 'Which protocol allows a router to discover information about directly connected devices?', CDP would be the correct answer as it is specifically designed for that purpose.
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 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓DNSCorrect answer▾
Why this is correct
The Domain Name System is the service that directly performs hostname-to-IP address resolution. When a client types a URL like www.cisco.com, it sends a DNS query to a resolver, which returns the corresponding IPv4 or IPv6 address. This is the fundamental name resolution service on which applications rely before establishing TCP connections. Without DNS, users would need to memorize numeric IP addresses.
✗ARPWrong answer — click to see why▾
Why this is wrong here
ARP (Address Resolution Protocol) operates at Layer 2 and resolves IPv4 addresses to MAC addresses within a local network segment. It does not perform hostname-to-IP resolution; instead, it maps an already-known IP address to a hardware address for data link layer communication.
★ When this WOULD be the correct answer
If the question asked about determining the MAC address of a device given its IP address within a local network, ARP would be the correct answer. For example, 'Which protocol is used to resolve an IP address to a MAC address on a local network?' would make ARP the right choice.
Why candidates choose this
Students may confuse ARP with DNS because both involve address resolution. However, ARP resolves IP to MAC, not hostname to IP, and is limited to local network communication.
✗NTPWrong answer — click to see why▾
Why this is wrong here
NTP (Network Time Protocol) is used to synchronize clocks between devices over a network. It does not provide any name resolution functionality; its sole purpose is time synchronization, which is critical for logging and authentication but unrelated to converting hostnames to IP addresses.
★ When this WOULD be the correct answer
If the exam question asked which service is responsible for synchronizing the time on a networked device, then NTP would be the correct answer. For example, a question could state, 'Which protocol ensures accurate timekeeping across devices in a network?'
Why candidates choose this
The acronym NTP might be confused with DNS due to both being network services, but their functions are entirely different. Students with partial knowledge might think NTP involves some form of lookup or resolution.
✗CDPWrong answer — click to see why▾
Why this is wrong here
CDP (Cisco Discovery Protocol) is a proprietary Layer 2 protocol used by Cisco devices to discover neighboring devices and learn about their capabilities, such as device type and IP addresses. It does not resolve hostnames to IP addresses for client applications.
★ When this WOULD be the correct answer
In a question asking about the identification of neighboring Cisco devices on a network, such as 'Which protocol allows a router to discover information about directly connected devices?', CDP would be the correct answer as it is specifically designed for that purpose.
Why candidates choose this
CDP's ability to provide IP addresses of neighboring devices might lead students to incorrectly assume it can resolve hostnames. However, CDP is a discovery protocol, not a name resolution service like DNS.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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 |
Go deeper
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Key term
ARP
Address Resolution Protocol (ARP) is a network protocol used to map a device's IP address to its physical MAC address so data can be delivered correctly on a local network.
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco 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 200-301 exam.