CCNA Network Services and Security Practice Question
A branch router should automatically learn the IP address of a time source so logs from all devices show matching timestamps. Which service provides that function?
⚠ Common exam trap
A common exam trap is selecting DNS as the answer because it involves IP addresses and network services, tempting candidates to confuse name resolution with time synchronization. Another trap is choosing TFTP, since it is a network protocol often associated with configuration and file transfers, misleading candidates to think it manages device settings including time. NetFlow might also confuse candidates because it deals with network traffic data, but it does not affect device clocks. The key is to recognize that only NTP is designed specifically to synchronize time across devices, which is critical for matching timestamps in logs.
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
✓
NTP
NTP synchronizes clocks across network devices. When timestamps line up, syslog messages and troubleshooting output become much more useful.
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 it's wrong here
DNS (Domain Name System) resolves human-friendly domain names to IP addresses, and while a router may receive a DNS server address via DHCP, that is not the purpose described here. The question targets automatic acquisition of a time source, not name resolution. Therefore, confusing DNS with NTP would leave the router's clock unsynchronized.
When this WOULD be correct
In a scenario where the question asks about a service that resolves hostnames to IP addresses for network devices, DNS would be the correct answer. For example, if the question focused on how devices can locate and communicate with each other using domain names, DNS would be the appropriate choice.
- ✓
NTP
Why this is correct
Network Time Protocol (NTP) provides automatic time synchronization by allowing a router to discover NTP servers via broadcast, multicast, or DHCP option 42. A branch router can thus learn the IP address of an authoritative time source without manual per-device configuration, ensuring consistent timestamps for logs and authentication. This is the correct service for the requirement.
- ✗
TFTP
Why it's wrong here
Trivial File Transfer Protocol (TFTP) is used to transfer configuration files or IOS images to and from a router, typically via a manually defined server address. TFTP does not offer any time synchronization functionality, nor does a branch router need to auto-discover a TFTP server for the stated purpose. Thus, it is unrelated to the requirement of automatically learning a time server's IP.
When this WOULD be correct
If the question were about a scenario where a router needs to download configuration files or firmware updates from a server, TFTP would be the correct answer, as it is specifically designed for simple file transfers in a network.
- ✗
NetFlow
Why it's wrong here
NetFlow is a traffic accounting and export mechanism that monitors flow statistics and sends them to a NetFlow collector. It does not involve automatically learning a server address for time synchronization; instead, the collector IP is explicitly configured. NetFlow provides visibility into network usage, not clock synchronization, making it an incorrect answer.
When this WOULD be correct
If the exam question asked about a service that analyzes and reports on network traffic patterns, or if it inquired about tools for monitoring network performance, then NetFlow would be the correct answer as it provides detailed traffic analysis.
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.
✓NTPCorrect answer▾
Why this is correct
Network Time Protocol (NTP) provides automatic time synchronization by allowing a router to discover NTP servers via broadcast, multicast, or DHCP option 42. A branch router can thus learn the IP address of an authoritative time source without manual per-device configuration, ensuring consistent timestamps for logs and authentication. This is the correct service for the requirement.
✗DNSWrong answer — click to see why▾
Why this is wrong here
DNS is primarily used for resolving domain names to IP addresses, not for synchronizing time across devices. Therefore, it does not fulfill the requirement of automatically learning a time source for timestamp consistency.
★ When this WOULD be the correct answer
In a scenario where the question asks about a service that resolves hostnames to IP addresses for network devices, DNS would be the correct answer. For example, if the question focused on how devices can locate and communicate with each other using domain names, DNS would be the appropriate choice.
Why candidates choose this
Candidates may confuse DNS with time synchronization services due to their roles in network functionality, leading them to mistakenly believe that DNS can also handle time-related tasks.
✗TFTPWrong answer — click to see why▾
Why this is wrong here
TFTP (Trivial File Transfer Protocol) is used for transferring files, not for synchronizing time across devices. It does not provide time synchronization services, which is the requirement in the question.
★ When this WOULD be the correct answer
If the question were about a scenario where a router needs to download configuration files or firmware updates from a server, TFTP would be the correct answer, as it is specifically designed for simple file transfers in a network.
Why candidates choose this
Candidates may confuse TFTP with other network services and mistakenly associate it with device management tasks, leading them to believe it could also handle time synchronization, despite its actual purpose.
✗NetFlowWrong answer — click to see why▾
Why this is wrong here
NetFlow is primarily used for collecting and monitoring network traffic data, not for synchronizing time across devices. It does not provide time source information necessary for matching timestamps in logs.
★ When this WOULD be the correct answer
If the exam question asked about a service that analyzes and reports on network traffic patterns, or if it inquired about tools for monitoring network performance, then NetFlow would be the correct answer as it provides detailed traffic analysis.
Why candidates choose this
Candidates may confuse NetFlow with time synchronization services due to its role in network management, leading them to incorrectly associate it with log timestamping functionalities.
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
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Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
Syslog
Syslog is a standard protocol used to send and store log messages from network devices and servers to a central logging server for monitoring and troubleshooting.
Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
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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.