Promoting a DC: Error determining whether the target environment require adprep


When you are promoting a new Domain Controller in to an existing Active Directory Forest/Domain, you let the default setting of “Any domain controller” to sync from and you are stuck at promotion process with this error message:

Error determining whether the target environment require adprep:  
Validation error Validation error: Unable to make an LDAP connection to server RandomDC01.company.com 
Exception: The specified server cannot perform the requested operation  Details: Test.VerifyForestUpgradeStatus.ADPrep.Win32Exception.-2147467259

If I choose a closest domain controller manually, you still the ‘freaking’ error message:

Error determining whether the target environment require adprep:
Validation error Validation error: Unable to check forest upgrade status for server ClosestDC1.company.com
Exception: The specified server cannot perform the requested operation
Details: Test.VerifyForestUpgradeStatus.ADPrep.Win32Exception.-2147467259

OK, now. What seems to be the ‘problem’? I believe the new server being promoted to a DC is NOT seeing the network or any domain controllers correctly. Check these few possible issues/solutions:

  1. Is the new server pings any other domain controllers? Can you Telnet port 389? Fix the Network card (IP, subnet or bad driver)
  2. Is any Firewall between the new server to existing domain controllers? Check here what firewall ports needs to open – https://support.microsoft.com/en-us/help/179442/how-to-configure-a-firewall-for-domains-and-trusts
  3. Is this new server a VM? check it is connected to correct (software) swtich/VLAN.

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