This LPIC-2 practice question tests your understanding of network client management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 runs an NTP server that should only synchronize with trusted upstream servers and provide time to internal clients. Which restrict clause in ntp.conf would best secure the server against unauthorized queries?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
restrict default ignore
Why wrong: Blocks all NTP packets, including time requests.
restrict default kod nomodify notrap nopeer noquery
Why wrong: Blocks all queries including time synchronization.
restrict 192.168.0.0 mask 255.255.0.0 nomodify notrap
Allows time synchronization from the subnet while blocking modifications.
restrict 127.0.0.1
Why wrong: Only allows localhost, not sufficient for clients.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
restrict 192.168.0.0 mask 255.255.0.0 nomodify notrap
Option C is correct because it uses a restricted subnet mask (192.168.0.0/16) to allow only internal clients to query the NTP server, while blocking unauthorized external queries. The `nomodify` and `notrap` flags prevent clients from altering the server's configuration or sending control message traps, which aligns with the requirement to secure the server against unauthorized queries. This approach ensures that only trusted internal hosts can synchronize time without exposing the server to external threats.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
restrict default ignore
Why it's wrong here
Blocks all NTP packets, including time requests.
restrict default kod nomodify notrap nopeer noquery
Why it's wrong here
Blocks all queries including time synchronization.
restrict 192.168.0.0 mask 255.255.0.0 nomodify notrap
Why this is correct
Allows time synchronization from the subnet while blocking modifications.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
restrict 127.0.0.1
Why it's wrong here
Only allows localhost, not sufficient for clients.
Common exam traps
The trap here is that candidates often choose option B because it includes many security flags, but they overlook that `restrict default` applies to all hosts not explicitly allowed, which would block the required upstream synchronization unless additional `restrict` lines are added for trusted servers.
Detailed technical explanation
The `restrict` clause in `ntp.conf` uses a mask to define a network range, and the `nomodify` flag prevents clients from changing the server's configuration via NTP control messages (e.g., `ntpq` or `ntpdc`), while `notrap` disables the trap facility used for remote event logging. In practice, a common misconfiguration is to use `restrict default ignore` without explicitly allowing trusted upstream servers via `restrict <upstream-IP>`, which can cause the server to drift over time. The `mask 255.255.0.0` in option C correctly restricts access to the 192.168.0.0/16 subnet, which is typical for internal corporate networks.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
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FAQ
Network Client Management — This question tests Network Client Management — Read the scenario before looking for a memorised answer..
The correct answer is: restrict 192.168.0.0 mask 255.255.0.0 nomodify notrap — Option C is correct because it uses a restricted subnet mask (192.168.0.0/16) to allow only internal clients to query the NTP server, while blocking unauthorized external queries. The `nomodify` and `notrap` flags prevent clients from altering the server's configuration or sending control message traps, which aligns with the requirement to secure the server against unauthorized queries. This approach ensures that only trusted internal hosts can synchronize time without exposing the server to external threats.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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