1.07.1Basic
A time-synchronization client queries a standard NTP server.
Use UDP transport.
Which destination port is used?
× Incorrect
NTP uses UDP port 123 by default. It is distinct from DNS 53 and web ports 80 and 443.
Detailed explanation
Incorrect53
Incorrect. 53 is DNS.
Incorrect. 53 is DNS.
Incorrect80
Incorrect. 80/tcp is HTTP.
Incorrect. 80/tcp is HTTP.
Correct123
Correct. NTP uses UDP port 123.
Correct. NTP uses UDP port 123.
Incorrect443
Incorrect. 443/tcp is HTTPS.
Incorrect. 443/tcp is HTTPS.
Try it yourself
An example you can run in a temporary verification environment.
getent services ntp | sed -n '1p'Expected result
ntp 123/udpを示すサービスデータベース行Key points
- NTP is 123/udp
- It is a time protocol
- Distinguish DNS and web ports
Notes
- Environment: Linux NSS servicesデータベース / 外部通信なし
- Command output formatting can vary slightly by distribution or tool version.
- Run the example in a temporary directory or process when possible.
Foundation review
Read the scope first
Check whether the command acts on the current shell, a new process, an existing process, or a file.
Verify the observable result
Use the supplied command and compare the output with the expected result.
Question IDKL-102-951
EnvironmentLinux NSS servicesデータベース / 外部通信なし
Last technical review2026-08-13
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