NTP clients not receiving updates

• Clients are not receiving NTP responses from the server
• Clients were previously synchronized, but have stopped receiving NTP updates
• Clients drift out of sync or report the NTP server as unreachable

Symptoms may vary depending on network configuration and environment.

• Network configuration prevents NTP traffic from reaching clients
• Clients are referencing an outdated or incorrect IP address for the NTP server. If the GMR is configured for DHCP, a network switch or DHCP server may assign a new IP address after a reboot or network change.
• Firewall rules are blocking NTP traffic (UDP port 123)
• NTP service is not running or has stopped unexpectedly
• The server is not synchronized to its reference source (for example, GPS lock is not achieved)

1. Confirm the NTP service is running on the GMR.
   If the service is stopped, clients will not receive time updates.
2. Verify the GMR is synchronized to a valid reference source.
   Check device status to confirm it is locked to GPS or another configured reference.
3. Check network connectivity between clients and the GMR.
   Confirm clients can reach the GMR over the network using tools such as ping or traceroute.
4. Verify firewall and security rules allow NTP traffic.
   Ensure UDP port 123 is permitted between the GMR and all NTP clients.
5. Confirm clients reference the GMR’s current IP address.
   Verify the configured server address matches the GMR’s current IP (especially if DHCP is enabled).

• Clients report successful synchronization
• NTP responses are received consistently
• Client system time remains stable

Time Dissemination During Reference Outages