Configure NTP Time Sync Using Group Policy – TheITBros (2023)

The Windows Time service is the basis for the normal functioning of the Active Directory domain. The W32Time service is essential for successful operationing of Kerberos authentication in AD. In the AD environment, the time synchronization is performed according to a domain hierarchy: domain-joined computers and servers get the time from the nearest domain controller on which they are logged on, all domain controllers synchronize their time with a single DC that holds the PDC Emulator FSMO role.

You need to configure your PDC Emulator (Primary Domain Controller) to sync time with a reliable external time source. The external time source is usually one or more public NTP (Network Time Protocol) servers, like time.windows.com or the NTP server of your provider.

How Does Time Sync Works in AD Domain?

This W32Time service on Windows is used to synchronize the time in the AD organization. A computer can be both a client and an NTP server. By default, domain computers synchronize time using the Windows Time service instead of NTP.

By default, the Windows Time Service in Active Directory is configured as follows:

• After performing a clean Windows installation, an NTP client is launched on the computer, which is synchronized with an external time source (time.windows.com);
• When you join PC to domain, the time sync setting changes. All client computers and member servers in the domain synchronize their time with AD domain controllers;
• When a member server is promoted to a domain controller, it can be used as a time source for domain computers. All domain controllers synchronize their time with a domain controller with the PDC emulator role;
• The PDC emulator is the main time server for the entire organization. It synchronizes with an external time source, or with the server’s hardware clock in CMOS/BIOS (this method of time synchronization is not recommended);
• This time synchronization scheme (according to the AD DS hierarchy) works properly in most cases and doesn’t require admin intervention. However, the structure of the time service in Windows may not follow the domain hierarchy.

If you are facing a problem when the time on clients and domain controllers is different, most likely your domain has a problem with time synchronization and then this article can be very useful for you.

First of all, it is necessary to select an NTP server you want to use. The list of public NTP atomic clock servers is available at http://ntp.org. In our example, we will use 0.us.pool.ntp.org, 1.us.pool.ntp.org, 2.us.pool.ntp.org, and 3.us.pool.ntp.org.

Configuring domain time synchronization using Group Policy consists of 2 steps:

1. Create a GPO for the domain controller with a PDC role;
2. Create a GPO for Windows client computers in the AD Domain.

Note. Check our tutorial on how to use ntpdate to sync time in Linux.

Configuring PDC Domain Controller to Sync Time with External NTP Server

First of all, you need to configure the PDC and enable the NTP service on it. To locate the name of the server with the PDC role in the domain, run the command:

netdom /query fsmo

Connect to the specified DC, open a command prompt, and run:

w32tm /query /source

If you see in the output:

• Local CMOS Clock — the time source on this server is its local hardware clock;
• VM IC Time Synchronization Provider — then your domain controller with the PDC role is a virtual machine that synchronizes the time with the host.

Disable time synchronization with the host via the registry:

• Set the Enabled parameter to 0 in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\VMICTimeProvider

or in the settings of the virtual machine (the screenshot below shows how to disable the time synchronization of the VM with the Hyper-V host using the Time Synchronization option in the Integration Services section).

If you are running a virtualized domain controller on VMware vSphere/ESXi, you can disable time sync in the virtual machine settings (Edit Settings > VM Options > VMware Tools > Time, uncheck the option Synchronize guest time with host).

Note. The virtual PDC emulator must always synchronize the time with an external source, and the time synchronization with the host must be disabled. This also applies to any other VMs joined to the domain.

The best approach is to configure the PDC emulator to synchronize the time directly with an external time source.

Check that the external NTP servers you have chosen are accessible from the primary domain controller (outbound port UDP 123 must be open to the target server). Get the current time from an external NTP server using the command:

w32tm /stripchart /computer:0.us.pool.ntp.org

In this example, the specified NTP server is available and you have successfully obtained the current time from it.

You can manually configure the time synchronization of the PDC host with an external NTP source using the w32tm.exe tool:

net stop w32timew32tm /config /syncfromflags:manual /manualpeerlist:"1.us.pool.ntp.org,0x8 1.us.pool.ntp.org,0x8 2.us.pool.ntp.org,0x8 3.us.pool.ntp.org,0x8"w32tm /config /reliable:yesw32tm /config /updatenet start w32time

Check your current configuration:

w32tm /query /configuration

Configure External NTP Source on PDC Domain Controller Using GPO

The PDC Emulator role can be transferred with PowerShell between domain controllers, so we need to make sure that GPO is applied only to the current holder of the Primary Domain Controller role. To do this, run the Group Policy Management Console (GPMC.msc). Select the WMI Filters section and create a new WMI filter with the name Filter PDC Emulator and the following WMI query in the root\CIMv2 namespace Select * from Win32_ComputerSystem where DomainRole = 5.

Create a new GPO and link it to the AD OU named Domain Controllers.

Select this GPO and switch to the Edit mode. Go to the following section of Group Policy Editor Console: Computer Configuration > Administrative Templates > System > Windows Time Service > Time Providers.

Enable the following policy settings:

• Configure Windows NTP Client: Enabled (policy settings are described below);
• Enable Windows NTP Client: Enabled;
• Enable Windows NTP Server: Enabled.

Specify the following settings in Configure Windows NTP Client policy:

• NtpServer: us.pool.ntp.org,0x1 1.us.pool.ntp.org,0x1 2.us.pool.ntp.org,0x1 3.us.pool.ntp.org,0x1;
• Type: NTP;
• CrossSiteSyncFlags: 2;
• ResolvePeerBackoffMinutes: 15;
• Resolve Peer BAckoffMaxTimes: 7;
• SpecilalPoolInterval: 3600;
• EventLogFlags: 0.

Note. Do not forget to configure your firewall properly and allow your PDC to access the external NTP servers over the NTP protocol (UDP port 123).

You can open the NTP port on Windows Defender Firewall using PowerShell:

New-NetFirewallRule -Name 'NTP_Server_123UDP' -DisplayName 'NTP Server Port' -Description 'Allow Inbound Connections to NTP Server' -Profile Any -Direction Inbound -Action Allow -Protocol UDP -Program Any -LocalAddress Any -LocalPort 123

Assign a WMI filter Filter PDC Emulator that you created earlier to the GPO.

It remains to update the Group Policy settings on PDC using gpupdate command:

gpupdate /force

Perform a manual time synchronization with your NTP source:

w32tm /resync

And check the current NTP settings:

w32tm /query /status

Run the command:

w32tm /monitor

When running on a domain controller, this command shows how much time is different between other domain controllers and the external time source for which the PDC is configured.

Tip. If something does not work, try to restart the Windows Time service and reset its configuration:

net stop w32timew32tm.exe /unregisterw32tm.exe /registernet stop w32tim

Configure Client Time Sync Settings Using GPO

By default in Active Directory, domain clients synchronize their time with domain controllers (option Nt5DS — synchronize time to domain hierarchy). Typically, this behavior does not need to be reconfigured. However, if there are problems with time sync on your domain clients, you can try to specify the time server directly on clients using GPO.

To do this, create a new GPO and assign it to the OU with computers. In the GPO Editor go to the following section Computer Configuration > Administrative Templates > System > Windows Time Service > Time Providers and enable the policy Configure Windows NTP Client.

As an NTP server specify the name of your domain (preferred) or IP address/FQDN of the PDC:

NTP Server: lon-dc1.adatum.com,0x9

Set Type: NT5DS

CrossSiteSyncFlags: 2
ResolvePeerBackoffMinutes: 15
ResolvePeerBackoffMaxTimes: 7
SpecialPollInterval: 3600
EventLogFlags: 0

Note. Possible values for the Type parameter:

• NoSync — the NTP server is not synchronized with any external time source. The system clock built into the server’s CMOS chip is used;

• NTP — the NTP server is synchronized with external time servers, which are specified in the NtpServer registry parameter (this is the default behavior on a stand-alone computer);

• NT5DS — the NTP server performs synchronization according to the domain hierarchy (used by default on domain-joined computers;

• AllSync — the NTP server uses all available sources for time synchronization.

Update Group Policy settings on the clients and check the received time sync settings as described above.

How to Manually Configure a Windows Client to Sync Time with NTP Server?

In this section, we will describe how to manually sync time to domain controller on Windows clients. You can use this guide to configure time synchronization on non-domain Windows computers.

First, reset all settings for the time service and remove the service:

w32tm /unregister

Restart the computer and then re-register the time service:

w32tm /register

Start the w32Time service:

net start w32Time

Configure the synchronization of the Windows client with the NTP server (your PDC):

w32tm /config /manualpeerlist:"lon-dc01.adatum.com,0x9" /syncfromflags:manual /reliable:yes /update

Restart the service:

net stop w32time && net start w32time

Update the time configuration settings:

w32tm /config /update

Synchronize the time:

w32tm /resync

Check the status:

w32tm /query /status

Enable automatic startup of the Time Service using PowerShell:

Set-Service –Name w32tm–StartupType Automatic

Hint. If you need to quickly synchronize your Windows device with an accurate time server, run:

net time \\your_ntp_server_name /set /y