There is no question about it, having accurate time in your environment set in critical infrastructure systems is a must. Many business-critical applications and infrastructure systems rely on accurate time synchronized between them to ensure the system functions as expected. Time skew can cause all kinds of weirdness when it is misconfigured or out of sync between different servers/systems. This is especially true in a Windows Server Active Directory domain. Having accurate time between a client computer and domain controllers is essential. Let’s take a look at how to set ntp server Windows 2016 or Windows 2019 to see how this can be easily carried out.
What is NTP?
Wen it comes to synchronizing time in most enviornments, Network Time Protocol (NTP) is the protocol that is used to ensure accurate time across your environent. In most environments, NTP servers, special time servers, are configured that provide an external time source for which your internal servers can synchronize with.
There are several widely known NTP IP addresses on the Internet that provide reliable time sources for your network. The NTP.org servers are one such set of time servers that provide an NTP source for configuration.
There are a few NTP values to be aware of:
- NTP Server – This is a specialized server that is able to detremine the precise time from an external timing reference such as GPS and passes these precise time values on to your network
- Offset – This is the difference in time between the external time server and the time on a local client computer. The larger the offset, the more inaccurate the timing source is.
- Delay – This is the value of the round-trip time (latency) of the timing message between the client to the server and back again.
How Time is synchronized in a Windows Server domain
In a Windows domain, Microsoft has default configuration in place that takes care of a good portion of the NTP configuration. Starting with Windows 2000 Server, Windows clients are configured as NTP Clients. When configured as an NTP client, Windows computers only attempt to contact the domain controller for NTP synchronization or a manually specified NTP server.
Microsoft has made the domain controller the default in a Windows domain since it makes sense that clients already have a secure channel established with DCs for other types of communications. Additionally, accurate and synchronized time between domain controllers and clients is especially important for all kinds of things such as logins, group policy synchronization and other tasks/operations.
The order of operations or hierarchy in a Windows domain is as follows:
- Domain members attempt to synchronize time with any domain controller located in the domain
- Domain controllers synchronize with a more authoritative domain controller
- The first domain controller that is installed in the environment is automatically configured to be a reliable time source.
- Other than the first domain controller installed, the PDC emulator (if role has been moved from the first DC installed) generally holds the position of best time source.
An important point to consider and that comes into play when thinking about why we set ntp server in Windows 2016 or Windows 2019 is the authoritative domain controller must have a reliable source to synchronize with as well. This is generally an external time server outside of the domain hierarchy.
Now that we know how the domain hierarchy for time is configured, how is the external time source configured on your domain controller that is configured as the reliable source of time?
Configuring Windows Time Service with W32tm.exe
When it comes to Windows Server environments like Windows Server 2016 or Windows Server 2019, there is a special Windows service that controls the time synchronization of your Windows hosts. This is the Windows Time Service.
Microsoft provides a command line tool to interact with the Windows Time Service called W32tm.exe. This has been included in Windows operating systems since Windows XP/Windows 2003 and later. It can be used to configure Windows Time service parameters as well as diagnose time service problems. This is generally the tool of choice when it comes to configuring, monitoring, and administering Windows Time.
Using the W32tm.exe utility is fairly straightforward. It can be used from a normal command prompt as well as from a PowerShell prompt. There are several command parameters included that allow not only configuring the NTP servers you want to query, but also parameters that allow viewing the low level registry configuration as well as the synchronization status.
You can read the official Microsoft KB on the Windows Time service and the W32tm.exe utility here:
However, there are a few commands I would like to show you for the purposes of configuring your Domain controller that is to be the reliable time source (PDC Emulator) for your domain.
The first command is the command line entry to specify your NTP servers, which in this case I am using the NTP.org servers to set as the source of my NTP synchronization.
w32tm /config /syncfromflags:manual /manualpeerlist:"0.us.pool.ntp.org 1.us.pool.ntp.org 2.us.pool.ntp.org 3.us.pool.ntp.org" /update Stop-Service w32time Start-Service w32time
If you want to view the status of the NTP synchronization on your server after you have configured the values and restarted the w32time service, you can use the following command:
w32tm /query /status
You can also check the values configured in your registry key hkey local machine system currentcontrolset services w32time config using the commands below. You can drill into the configuration parameters using the /dumpreg /subkey command.
w32tm /dumpreg w32tm /dumpreg /subkey:parameters
As shown, you can easily set NTP Server Windows 2016 or Windows 2019 using the w32tm command utility that allows interacting with the time service in Windows Server.
In a Windows domain, you want to configure your authoritative time source domain controller, which by default is the PDC Emulator, to pull time information from an authoritative source like NTP.org or some other reliable NTP time server.
After configuring the time source, the other domain controllers will synchronize with this server and then the Windows clients joined to the domain will synchronize with the domain controllers that have the corrected time from the authoritative server.