If you need to verify that Windows Computers/Servers are activated against KMS server by manually specified KMS server and port use following PowerShell command:

Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SoftwareProtectionPlatform" | Select-Object KeyManagementServiceName,KeyManagementServicePort

If values are empty, Windows is activated automatically by DNS record.

This is useful to know in case you plan to migrate KMS server to different IP address and system administrator specified KMS manually which can cause issues if you changed IP address of KMS server.

To clear out manual configuration of KMS run in CMD as Admin:

slmgr /ckms

To specify manually KMS server run in CMD as Admin:

slmgr /skms [IP ADDRESS or Hostname]:[PORT]
Example: slmgr /skms 192.168.1.100:1688