The answer is that the NTP server is unsynchronized or unreachable. This is the most likely cause because NTP clock synchronization depends entirely on IP reachability between the client switch and the time source; if the server is blocked by a routing issue or ACL, the switch cannot update its clock and will revert to its local hardware clock, which drifts over time. On the CCNA 200-301 v2 exam, this question tests your understanding that NTP is a client-server protocol requiring basic Layer 3 connectivity, not a Layer 2 or application-layer dependency—a common trap is assuming NTP needs a trunk port or DNS, but it works across any VLAN with a routable IP and can use an IP address directly. Remember the memory tip: NTP needs a path, not a name or a trunk.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: nTP requires IP reachability to a synchronized time source to update the local device clock accurately.. 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.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The NTP server is unsynchronized or unreachable
This is correct because NTP requires a reachable, synchronized time source. If the server is unreachable or not synchronized, the switch cannot update its clock, leading to drift.
B
The device must run Syslog before NTP can sync
Why wrong: Syslog is unrelated.
C
NTP requires a trunk port on the management VLAN
Why wrong: NTP needs IP reachability, not a trunk specifically.
D
The clock can sync only if DNS is configured
Why wrong: NTP uses IP connectivity; DNS is optional if using addresses.
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.
Key principle: NTP requires IP reachability to a synchronized time source to update the local device clock accurately.
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
This is correct because NTP requires a reachable, synchronized time source. If the server is unreachable or not synchronized, the switch cannot update its clock, leading to drift.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
NTP requires IP reachability to a synchronized time source to update the local device clock accurately.
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 needs IP reachability, not a trunk specifically.
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
NTP uses IP connectivity; DNS is optional if using addresses.
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
This is correct because NTP requires a reachable, synchronized time source. If the server is unreachable or not synchronized, the switch cannot update its clock, leading to drift.
✗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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
Network Time Protocol (NTP) is a critical IP service used to synchronize the clocks of network devices to a reliable time source. Accurate timekeeping is essential for logging, security protocols, and time-sensitive applications. NTP operates by exchanging timestamped packets between clients and servers, adjusting the local clock to match the server’s time. Cisco devices use NTP to maintain consistent time across the network, which is vital for troubleshooting and event correlation.
For NTP to function correctly, the client device must have IP reachability to a synchronized NTP server. This means the server must be reachable via routing and not blocked by access control lists (ACLs). The NTP server must itself be synchronized to a valid time source, indicated by a stratum level less than 16. If the server is unreachable or unsynchronized (stratum 16), the client device cannot update its clock and will continue to drift, showing incorrect time.
A common exam trap is assuming that enabling NTP configuration alone guarantees synchronization. In reality, network connectivity issues, ACLs blocking UDP port 123, or an unsynchronized NTP server cause the device to keep its local clock, which can be minutes off. Practical troubleshooting involves verifying NTP status, checking stratum levels, and ensuring IP connectivity to the NTP server. Understanding these behaviors helps avoid misdiagnosing unrelated features like Syslog, VLAN trunks, or DNS as causes of NTP sync failure.
KKey Concepts to Remember
NTP requires IP reachability to a synchronized time source to update the local device clock accurately.
A device configured with an unreachable or unsynchronized NTP server will retain its local clock, causing time drift.
NTP stratum levels indicate the distance from the authoritative time source; stratum 16 means no valid time source is reachable.
ACLs or routing issues can block NTP packets, preventing synchronization even if the server is configured.
Syslog is unrelated to NTP synchronization and does not affect the device’s ability to sync time.
NTP synchronization depends on IP connectivity, not on VLAN trunking or specific VLAN configurations.
DNS is optional for NTP if IP addresses are used directly; lack of DNS does not prevent NTP sync.
Monitoring NTP status commands helps verify synchronization state and troubleshoot connectivity or configuration issues.
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
NTP requires IP reachability to a synchronized time source to update the local device clock accurately.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review nTP requires IP reachability to a synchronized time source to update the local device clock accurately., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — NTP requires IP reachability to a synchronized time source to update the local device clock accurately..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 200-301 question wrong?
Review nTP requires IP reachability to a synchronized time source to update the local device clock accurately., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
NTP requires IP reachability to a synchronized time source to update the local device clock accurately.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which protocol is most directly responsible for keeping device clocks synchronized across a network?
medium
✓ A.NTP
B.TFTP
C.DHCP
D.CDP
Why A: The correct protocol is NTP. In plain language, NTP helps devices agree on the current time so that logs, authentication events, monitoring data, and troubleshooting records line up accurately. Without consistent time, a network team may see events from multiple devices but be unable to reconstruct the actual sequence correctly.
This matters more than many people realize because accurate time underpins many operational workflows. Syslog messages, security events, and monitoring alerts become much easier to trust when devices are synchronized. DHCP, TFTP, and CDP are useful for other purposes, but they do not exist to align device clocks. NTP is the protocol specifically associated with time synchronization.
Last reviewed: May 17, 2026
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