- A
The NTP server is not configured to respond to NTP requests from this client.
Ping works, but NTP uses UDP 123; the server may be configured to deny service to this client, or the server's NTP service is not running.
- B
The router's 'ntp source' command is missing, causing NTP packets to use an incorrect source IP.
Why wrong: While possible, the 'ntp source' command is optional; the router will use the egress interface IP, which should be reachable. The server being unreachable for NTP is more specific.
- C
The router's clock is set too far in the future, causing NTP to reject the server's time.
Why wrong: NTP can adjust large time differences, but the router would still show the server as reachable; the issue is no reachability at all.
- D
The router has 'ntp authenticate' enabled without the proper key.
Why wrong: If authentication were mismatched, the association would show as 'configured' but not synchronized; the server would still show reachability.
Quick Answer
The answer is that the NTP server is not configured to respond to NTP requests from this client. While the router can ping the server, NTP relies on UDP port 123, and reachability via ICMP does not guarantee that the NTP service is listening or permitted. The `show ntp associations` output showing the server in `.INIT.` state with zero reachability confirms that no NTP packets have been exchanged, even though the network path is up. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to distinguish between basic IP connectivity and application-layer service availability—a common trap where candidates assume ping success equals NTP success. Remember that NTP synchronization requires both the server to be configured to serve time and the client’s source interface to be correct; a missing `ntp server` statement or an ACL blocking UDP 123 on either side will leave the clock unsynchronized. Memory tip: “Ping is not NTP—reachability does not mean service.”
300-410 Device Management Practice Question
This 300-410 practice question tests your understanding of device management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An engineer is troubleshooting a router that is configured as an NTP client. The router's clock is not synchronizing with the NTP server at 192.168.1.1. 'show ntp status' shows 'clock is unsynchronized', and 'show ntp associations' shows the server as '.INIT.' with no reachability. The engineer can ping the NTP server. What 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.
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 not configured to respond to NTP requests from this client.
The NTP server may be reachable via ping, but NTP uses UDP port 123. The router may have an ACL blocking NTP traffic, or the NTP server may not be responding. However, a common issue is that the NTP server is not configured to serve time to the client, or the client's NTP source interface is incorrect.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 not configured to respond to NTP requests from this client.
- ✗
The router's 'ntp source' command is missing, causing NTP packets to use an incorrect source IP.
Why it's wrong here
While possible, the 'ntp source' command is optional; the router will use the egress interface IP, which should be reachable. The server being unreachable for NTP is more specific.
- ✗
The router's clock is set too far in the future, causing NTP to reject the server's time.
Why it's wrong here
NTP can adjust large time differences, but the router would still show the server as reachable; the issue is no reachability at all.
- ✗
The router has 'ntp authenticate' enabled without the proper key.
Why it's wrong here
If authentication were mismatched, the association would show as 'configured' but not synchronized; the server would still show reachability.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Trap categories for this question
Command / output trap
While possible, the 'ntp source' command is optional; the router will use the egress interface IP, which should be reachable. The server being unreachable for NTP is more specific.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.
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FAQ
Questions learners often ask
What does this 300-410 question test?
Device Management — This question tests Device Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The NTP server is not configured to respond to NTP requests from this client. — The NTP server may be reachable via ping, but NTP uses UDP port 123. The router may have an ACL blocking NTP traffic, or the NTP server may not be responding. However, a common issue is that the NTP server is not configured to serve time to the client, or the client's NTP source interface is incorrect.
What should I do if I get this 300-410 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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Last reviewed: Jun 18, 2026
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