- A
Add an iptables rule on the affected server to accept outbound UDP packets to 10.0.0.100 port 123.
Correct: The client's firewall is dropping outbound NTP packets; allowing them enables the client to reach the server and receive time synchronization.
- B
Remove the line 'restrict 10.0.0.100' from /etc/ntp.conf.
Why wrong: The restrict line limits the operations that 10.0.0.100 can perform (e.g., query), but it does not block network traffic; the real issue is the firewall.
- C
Modify the NTP server's firewall to allow inbound NTP from 10.0.1.0/24.
Why wrong: This would fix the issue eventually, but it is not something the administrator can do directly on the affected server; it requires network team coordination and is not the most direct action.
- D
Add a static route on the affected server for 10.0.0.100 via a different gateway.
Why wrong: There is no indication of network reachability issues; the problem is the firewall, not routing.
LPIC-1 Essential System Services and Networking Practice Question
This LPIC-1 practice question tests your understanding of essential system services and networking. 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.
A company manages a cluster of 50 web servers running Ubuntu 20.04. The servers are configured to synchronize time with an internal NTP server at 10.0.0.100 using the default ntpd. The NTP server itself syncs with external stratum 2 servers. Recently, the security team implemented a restrictive iptables firewall on all servers, allowing only essential services. Several servers in the 10.0.1.0/24 network now report time drift and ntpq -p shows all peers with '?' status. A network engineer runs tcpdump on one affected server and sees no NTP replies from 10.0.0.100. The NTP server's firewall is configured to allow inbound NTP from 10.0.0.0/24 only. The engineer also notes that the server's /etc/ntp.conf contains the line 'restrict 10.0.0.100' (which is incorrect) and that ntpq -crv shows 'sync target not reachable'. Which single action will most directly resolve the synchronization issue for the affected servers?
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
Add an iptables rule on the affected server to accept outbound UDP packets to 10.0.0.100 port 123.
The problem is that the NTP client's firewall on the affected servers (10.0.1.0/24) is blocking outbound NTP traffic, and the server's firewall is correctly blocking inbound from non-10.0.0.0/24. The incorrect 'restrict 10.0.0.100' line in ntp.conf is irrelevant because it only restricts the role of that IP (as a client) and does not block traffic. Adding an ACCEPT rule for outbound UDP 123 to the NTP server on the client's iptables will allow the client to send requests and receive replies. Changing the NTP server's firewall to allow 10.0.1.0/24 is a longer-term fix but not a direct action on the affected server. Modifying ntp.conf to remove the restrict line won't help with the firewall block. Adding a static route is irrelevant.
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.
- ✓
Add an iptables rule on the affected server to accept outbound UDP packets to 10.0.0.100 port 123.
- ✗
Remove the line 'restrict 10.0.0.100' from /etc/ntp.conf.
Why it's wrong here
The restrict line limits the operations that 10.0.0.100 can perform (e.g., query), but it does not block network traffic; the real issue is the firewall.
- ✗
Modify the NTP server's firewall to allow inbound NTP from 10.0.1.0/24.
Why it's wrong here
This would fix the issue eventually, but it is not something the administrator can do directly on the affected server; it requires network team coordination and is not the most direct action.
- ✗
Add a static route on the affected server for 10.0.0.100 via a different gateway.
Why it's wrong here
There is no indication of network reachability issues; the problem is the firewall, not routing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 practitioner preparing for the LPIC-1 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which LPIC-1 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Essential System Services and Networking — study guide chapter
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FAQ
Questions learners often ask
What does this LPIC-1 question test?
Essential System Services and Networking — This question tests Essential System Services and Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add an iptables rule on the affected server to accept outbound UDP packets to 10.0.0.100 port 123. — The problem is that the NTP client's firewall on the affected servers (10.0.1.0/24) is blocking outbound NTP traffic, and the server's firewall is correctly blocking inbound from non-10.0.0.0/24. The incorrect 'restrict 10.0.0.100' line in ntp.conf is irrelevant because it only restricts the role of that IP (as a client) and does not block traffic. Adding an ACCEPT rule for outbound UDP 123 to the NTP server on the client's iptables will allow the client to send requests and receive replies. Changing the NTP server's firewall to allow 10.0.1.0/24 is a longer-term fix but not a direct action on the affected server. Modifying ntp.conf to remove the restrict line won't help with the firewall block. Adding a static route is irrelevant.
What should I do if I get this LPIC-1 question wrong?
Identify which LPIC-1 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 24, 2026
This LPIC-1 practice question is part of Courseiva's free LPI 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 LPIC-1 exam.
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