Fast Troubleshooting for Windows Time Service (w32time) Synchronization

Hi! You have landed here most probably while searching for solution to your NTP synchronization problem, right? For your comfort, this page is excellent to start with. We've provided a list of the most common causes of NTP time sync troubles. Check which one applies yours and follow the proposed steps to make time service successful. We hope you will find these guidelines helpful!

Firewall or port filter blocking NTP packages

One reason for NTP synchronisation problems may be a firewall or port filter that is blocking the ports the programs use to communicate (by default UDP port 123). For example in Windows 8, check firewall settings in Control Panel -> Windows Firewall->Advanced settings. If the firewall is on, one has to enable Inbound and Outbound Rules for "Specific local ports" in our case UDP, port 123. For details of Windows firewall port settings, click on Figure 1,2 and 3.

Figure 1: Windows 8 Firewall, Advanced Settings.

Figure 2: Configuring the Inbound port rule in Windows 8.

Figure 3: Configuring the Outbound port rule in Windows 8.

Some w32time versions are unable to query time from NTP servers

Especially those coming with Windows XP or Windows Server 2003, may be (by default) unable to query the time from some NTP servers. Depending on the type of the Windows PC (e.g. standalone server or domain controller), NTP servers may not respond to the type of queries sent by w32time. w32time sends namely symmetric active instead of client mode packets to a NTP server. This problem has not been observed with the w32time version which has been shipped with Windows 2000, only with later versions.

Using some commands in a command line window, the behavior of w32time can be changed so that w32time sends the correct "client" mode request packets. The changes are saved permanently in the Windows registry.

To make any w32time changes in command line window one has to run cmd program as administrator (see Figure 4).

Figure 4: Run cmd program as administrator.

Then enter the following commands (Figure 5):

w32tm /config /manualpeerlist:[server],0x8 /syncfromflags:MANUAL
The actual IP address of the NTP server or its host name must be entered instead of [server].
The flag "0x8" forces w32time not to send "symmetric active" packets but normal "client" requests which the NTP server replies to as usual.

Then the following command can be used to immediately make the changes effective:

w32tm /config /update
If this command has completed successfully your system clock has synchronized to the given NTP server. To check it open a Date and Time window (click "time" icon in the lower right corner of the desktop) -> Change date and time settings -> Internet Time. You should see something similar to Figure 6.

Alternatively, the w32time service can be restarted:

net stop w32time net start w32time

The command:

net time /querysntp
can be used to check the configuration. The output should look similar to the line below:

The current SNTP value is:[server],0x8

If the w32time service is restarted it sends immediately a request to the NTP server. Additionally, the command:

w32tm /resync
can be used to let w32time send a request.

Figure 5: w32time behavior adjustment.

Figure 6: Windows Date and Time synchronized successfully.

Check if w32time service is running

Note that w32time service may only be enabled when no other ntp daemon is installed on your system. Otherwise the two services come into conflict. To check if w32time is running, do the following: go to Control Panel->Administrative Tools->Services. Scroll to "Windows Time" feature and check its "Status", which should be on "running". Check also the "Startup Type" and set it to "Automatic" or "Manual" if possible.

If the status of the Windows Time is currently not shown, then right click and choose Properties to open "Windows Time Properties (Local Computer)" window. In the Service status click on the "Start" button to start the time service. The result should resemble Figure 7.

Figure 7: w32time service settings.

Select a reliable NTP server

A great deal of synchronization problems may be caused by network break downs, unpredicted traffic delays, unknown accuracy and public NTP servers where you don't have control over. Although public time service may be cost free, but 24/7 operation, accuracy and customer support in case of a failure is not guaranteed. Therefore, if you consider issues like accuracy, reliability and security important for your network, an independent NTP/SNTP server is strongly recommended alternative to do the job.

Meinberg high quality time servers offer a broad spectrum of time synchronization solutions for networks of any size and industries. All the products are developed and manufactured in our plant located in Bad Pyrmont, Germany.

For more information on time servers visit our NTP server product portfolio

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