CCNA Network Services and Security Practice Question
Exhibit
show ntp associations address ref clock st when poll reach delay offset disp *~10.10.50.5 .INIT. 16 - 64 0 0.000 0.000 16000 Configured server: 10.10.50.5
A switch shows a clock that is several minutes off from other devices even though an NTP server has been configured. Which issue is the most likely cause?
⚠ Common exam trap
A common mistake is thinking that unrelated services like Syslog, trunk ports, or DNS are prerequisites for NTP; only IP connectivity to a synchronized NTP server matters.
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
✓
The NTP server is unsynchronized or unreachable
NTP requires IP reachability to the time source. If the NTP server is unreachable due to routing or ACL issues, the switch falls back to its local clock, causing drift. Option A is correct. Option B is wrong because Syslog has no effect on NTP synchronization. Option C is incorrect because NTP does not require a trunk port; it can operate over any VLAN with IP connectivity. Option D is false because DNS is only needed if the NTP server is specified by hostname; the server can be reached by IP address without DNS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The NTP server is unsynchronized or unreachable
Why this is correct
NTP clients trust time only from a server that is both reachable and itself synchronized to a reference clock. When the server is unreachable (e.g., UDP 123 is filtered) or its stratum is too high because it lost its upstream source, the switch discards the NTP packets and retains the local clock, which drifts after several minutes. The remedy is to verify the server's stratum and reachability before adjusting anything else.
- ✗
The device must run Syslog before NTP can sync
Why it's wrong here
Syslog and NTP are entirely separate services: syslog forwards log messages to a collector, while NTP synchronizes wall-clock time. The switch will happily update its clock from an NTP server even if no syslog server is defined, and the absence of syslog configuration cannot stop the NTP process. Mixing these protocols to explain clock drift is a category error.
When this WOULD be correct
In a different question scenario where a device is configured to log events via Syslog, and the exam asks about prerequisites for time synchronization, this option could be correct if the question indicated that Syslog must be operational for NTP to function correctly in that specific context.
- ✗
NTP requires a trunk port on the management VLAN
Why it's wrong here
NTP is an application-layer protocol that rides on IP and UDP port 123; a trunk port is an Ethernet feature for multiplexing multiple VLANs onto a single link. The switch only needs an IP address in any VLAN that provides a route to the NTP server, whether that VLAN is untagged or trunked. If the clock is off, trunking is completely irrelevant to the failure.
When this WOULD be correct
In a different exam scenario where the question specifies that NTP traffic must traverse a trunk port due to VLAN segmentation, and the switch is misconfigured to not allow NTP on that trunk, this option could be correct.
- ✗
The clock can sync only if DNS is configured
Why it's wrong here
A switch can synchronize its clock to an NTP server using the server's numeric IP address, which requires no name resolution. DNS is only a convenience when the configuration references a hostname like 'time.example.com' instead of an IP. If the clock is off, the root cause must be reachability or synchronization of the NTP server, not a missing DNS record.
When this WOULD be correct
In a different scenario where a question states that a device is unable to resolve the NTP server's hostname due to DNS misconfiguration, option D would be correct. This would imply that the device cannot reach the NTP server at all, thus failing to sync its clock.
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.
✓The NTP server is unsynchronized or unreachableCorrect answer▾
Why this is correct
NTP clients trust time only from a server that is both reachable and itself synchronized to a reference clock. When the server is unreachable (e.g., UDP 123 is filtered) or its stratum is too high because it lost its upstream source, the switch discards the NTP packets and retains the local clock, which drifts after several minutes. The remedy is to verify the server's stratum and reachability before adjusting anything else.
✗The device must run Syslog before NTP can syncWrong answer — click to see why▾
Why this is wrong here
Syslog and NTP are independent; Syslog is not a prerequisite for NTP synchronization.
★ When this WOULD be the correct answer
In a different question scenario where a device is configured to log events via Syslog, and the exam asks about prerequisites for time synchronization, this option could be correct if the question indicated that Syslog must be operational for NTP to function correctly in that specific context.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of the relationship between logging and time synchronization, believing that logging services must be active for NTP to function properly, reflecting a common misconception in network management.
✗NTP requires a trunk port on the management VLANWrong answer — click to see why▾
Why this is wrong here
NTP operates over any VLAN with IP connectivity; a trunk port is not required.
★ When this WOULD be the correct answer
In a different exam scenario where the question specifies that NTP traffic must traverse a trunk port due to VLAN segmentation, and the switch is misconfigured to not allow NTP on that trunk, this option could be correct.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of VLAN configurations and their impact on network services, leading them to incorrectly associate trunk ports with NTP functionality.
✗The clock can sync only if DNS is configuredWrong answer — click to see why▾
Why this is wrong here
DNS is only needed if the NTP server is specified by hostname; the server can be reached by IP address without DNS.
★ When this WOULD be the correct answer
In a different scenario where a question states that a device is unable to resolve the NTP server's hostname due to DNS misconfiguration, option D would be correct. This would imply that the device cannot reach the NTP server at all, thus failing to sync its clock.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of how NTP operates, believing that hostname resolution is a prerequisite for synchronization, especially if they have encountered scenarios where DNS issues affected other services.
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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Key term
Network Time Protocol
Network Time Protocol (NTP) is a networking protocol that synchronizes the clocks of computers and devices over a network to a common reference time source, typically Coordinated Universal Time (UTC).
Key term
Fully Qualified Domain Name
A Fully Qualified Domain Name is the complete and unambiguous website or server name that includes the host, domain, and top-level domain, leaving no room for guesswork.
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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.