Port 123 — NTP
Quick reference for TCP/UDP port 123, used by NTP. Includes what the service does, security guidance and related ports.
Port
123
Protocol
UDP
Service
NTP
What is port 123?
Network Time Protocol for clock synchronization.
What port does NTP use?
NTP listens on port 123 by default.
Security guidance
Medium risk — open with care
Port 123 (NTP) can safely face the internet if you keep the software up to date, restrict admin endpoints, and use TLS where possible. Audit who can reach it and watch your logs.
Related ports
Frequently asked
What is port 123 used for?+
Port 123 is the standard TCP/UDP port for NTP. Network Time Protocol for clock synchronization.
What port does NTP use?+
NTP listens on port 123 by default.
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