I’m using a RUT956 as an NTP server for a Phoenix Contact PLC on the LAN.
The router has a GPS module connected and the system time is correctly synchronized from the GPS signal (the time displayed on the router is accurate).
However, even though the system clock is synchronized via GPS, the internal NTP server (untpd) still reports itself as unsynchronized (stratum 16).
Because of this, the PLC refuses to use the router as a valid NTP source.
In summary:
- GPS is enabled and the router successfully synchronizes its own time via GPS
- The system clock is correct
- The NTP server never leaves the unsynchronized state
- LAN clients see the router as stratum 16 and cannot synchronize
It looks like untpd does not recognize GPS‑based time as a valid synchronization source, even though the device clearly has the correct time.