The port 123/UDP…. is used by…NTP To synchronize the time between equipment, servers and workstations. A consistent time is essential to many mechanisms of authentication, logging and correlation of events; this sheet presents useful controls before of authorize or troubleshooting this flow….
What is Port 123 for?…
The port 123/UDP…. NTP uses it to synchronize the time. A time drift can affect logs, certificates and mechanisms of authentication; in Active Directory, a consistent hour is important for Kerberos. Posts must therefore use a controlled time hierarchy rather than randomly selected sources…
The port can be reached without the selected source, stratum or time difference being correct….
Transport Protocol
UDP
Safety precautions
Should we open this port in the firewall?
Allow NTP to clearly identified sources of trust. An internal server does not need to be a public NTP service unless it is voluntary. Limit the administration requests, and unnecessary functions of the NTP daemon, monitor source changes and avoid mixing several uncoordinated time references….
How do I check this port?
On Windows, use…w32tm /query /status and…. w32tm /query /source to know the state and source…w32tm /stripchart /computer:SERVER /dataonly /samples:5 helps to observe the deviation with a source. On Linux, depending on the service installed,…chronyc sources -v or the NTP tools of the distribution allow to check the peers….
- Identify the actual time source used….
- Control DNS resolution, route and UDP 123…
- Compare the deviation and time department logs…
- Correct hierarchy before forcing repeated resynchronizations…
FAQ — port 123 / NTP….
Why is port 123 answering, but time is wrong?….
The source can be reached but not selected, in error, too far away or replaced by another source. Check the time service status, not just the network….
Does NTP use TITLE?….
The current NTP operation of this plug uses UDP 123….
What is the link between NTP and Active Directory?…
A consistent time is needed for several AD mechanisms, including Kerberos, to function properly. The time hierarchy must therefore be controlled…