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NTP behavior explained

 

Information

 

Summary:

Description of NTP daemon behavior and configuration.

Environment:

Product: Flowmon OS

Version: Any

Platform: Any

Question/Problem Description:

How often is Flowmon polling NTP servers?

Steps to Reproduce:  
Error Message:  
Defect Number:  
Enhancement Number:  
Cause:  
Resolution:

Flowmon OS uses NTP daemon ntpd. The polling interval of NTP servers is 64 seconds. Intervals shorter than 64 seconds should generally not be used with public servers on the Internet because it might be considered abuse. It might also take some time to restart the NTP daemon, poll the NTP server, and choose the primary one.

NTP daemon automatically chooses the primary NTP server to synchronize with. The algorithm is described in RFC 5905.

NTP configuration can be verified via CLI with the following commands:

ntpq -pn
timedatectl
ntpstat

When the NTP server is changed, the following components are restarted:

  • nfsen (flow collection/processing backend),
  • httpd (Apache web server),
  • PostgreSQL (database).

The nfsen restart might cause a gap in the flow collection.

If the NTP servers are changed successfully, the restarts are performed.
If the NTP server is not a valid IP/hostname (e.g., 1.2.3.500 or "invalid?hostname"), nothing is restarted.
If the NTP server is a valid IP/hostname but is not reachable, the configuration is saved, and restarts are performed.

Workaround:  
Notes: https://www.rfc-editor.org/rfc/rfc5905.html

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