Question 693 of 2,152

Device Management →hardMultiple ChoiceObjective-mapped

Troubleshooting NTP Client Synchronization Issues on Cisco Routers

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.

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.

Full breakdown with real-world context →

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.”

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 '.INIT.' state in 'show ntp associations' indicates that the client has sent NTP packets to the server but has not received any valid NTP responses. Since the engineer can ping the server, Layer 3 connectivity is fine, ruling out network issues. The most likely cause is that the NTP server is not configured to respond to requests from this client, either due to an access control list (ACL) on the server, a 'restrict' statement denying the client, or the server not being configured as an NTP server at all.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.
Why this is correct
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
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: answer the scenario, not the keyword

Cisco often tests the distinction between client-side and server-side issues; the trap here is that candidates assume a reachable ping means NTP should work, but NTP uses a different protocol (UDP 123) and can be filtered or restricted independently of ICMP.

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

NTP uses UDP port 123, and the client sends a mode 3 (client) packet to the server, which responds with a mode 4 (server) packet. The '.INIT.' state means the client has sent a packet but received no response; this can be due to a server-side ACL, a 'restrict' statement (e.g., 'restrict 192.168.1.1 mask 255.255.255.255 no serve'), or the server not running NTP. In real-world scenarios, NTP servers often have 'restrict default ignore' and then explicitly permit specific clients, so a missing permit for the client's IP would cause this exact symptom.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

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

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 300-410 question test?

Device Management — This question tests Device Management — Read the scenario before looking for a memorised answer..

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 '.INIT.' state in 'show ntp associations' indicates that the client has sent NTP packets to the server but has not received any valid NTP responses. Since the engineer can ping the server, Layer 3 connectivity is fine, ruling out network issues. The most likely cause is that the NTP server is not configured to respond to requests from this client, either due to an access control list (ACL) on the server, a 'restrict' statement denying the client, or the server not being configured as an NTP server at all.

What should I do if I get this 300-410 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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?

Read the scenario before looking for a memorised answer.

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