Network Time Clients Will Not Sync To The NTP Server

SR and SC Series NTP Servers Help and Support: Network Time Clients Will Not Sync To The NTP Server
Models that this article applies to:

SR Series: SR7110, SR9210, SR9750, SR9850, SR9860D
SC Series: SC7105, SC9205, SC9705


There are a number of reasons why a network time client may not synchronize to a NTP server. Here’s a few pointers:


1. When the SR and SC series NTP servers power-up they enter an unsynchronized state. Network time clients will not synchronize to the NTP server in this state. The NTP server need to synchronize and calibrate its own internal clock before any client will synchronize. In order to synchronize an NTP server, an external time reference is required, such as GPS or radio. When a GPS lock or a good radio signal is available, the time server will take a further 10 or 15 minutes to synchronize. See the ‘GPS Troubleshooting’ and ‘LF Radio Troubleshooting’ articles for more information on GPS and radio installation problems.

2. If the unit has been powered down for an extended period of time, its system time may have drifted too far from the correct time to synchronize. See ‘Incorrect Time or Bad Time Reported’ article to manually adjust the system time.

3. If the NTP server has lost GPS lock or radio signal for an extended period of time, it will also enter an unsynchronized state. Ensure a GPS lock or good radio signal is being received.

4. The time client needs to point to the IP address of the NTP server to synchronize. Ensure that the network time client is correctly pointing to the IP address of the NTP server.

5. Ensure that there is a physical network path between the client and NTP server. Ping the IP address of the NTP server from the client to ensure availability.

6. Check that there is no firewall between the client and server which could block NTP packets. This includes both firewall’s embedded in network infrastructure and software firewall’s installed on the client, such as Windows firewall. NTP uses UDP port 123 for communication between server and client – if you have a firewall, ensure this port is left open.

7. Only a single instance of an NTP or SNTP client can run on any one machine. In Windows, if you are using TimeTools NTP client or any other third-party client software then ensure that the ‘Windows Time Service’, w32time, is disabled in the service list.