Migrate from Windows Server 2012 R2 to Windows Server 2025

Question

Hello everyone,

I have a question about migrating all data, including GPO, DNS, DHCP, user domain accounts, user home directories, and other folders and files, from an old server running Windows Server 2012 R2 to Windows Server 2025.

Windows Server 2025 is set to be released this year, and I would like to migrate my old server to the new one.

Currently, I have one domain with a single domain controller. There are a few accounts, some GPO settings, user home directories, and various user files. I downloaded the Windows Server 2025 Standard Evaluation for testing. On the new Windows Server 2025, I installed DNS, DHCP, and AD DS, and tried to promote it to a domain controller. At this step, I selected "Add a domain controller to an existing domain" because I intended to add the new server, transfer all data and settings from the old one, and then decommission the old server. However, when I clicked "Next," I received the error: "Verification of replica failed. The forest functional level is not supported. To install a Windows Server 2025 domain or domain controller, the forest functional level must be Windows Server 2016 or higher."

I found online that I first need to upgrade the forest functional level and domain schema on the old server (Windows Server 2012 R2). I mounted the Windows Server 2025 ISO on the old server and ran the commands .\adprep.exe /forestprep and .\adprep.exe /domainprep. Everything seemed fine; the domain schema was updated from version 69 to 91 (I also restarted the old server). However, when I tried to add the Windows Server 2025 as a domain controller, I encountered the same error ("Verification of replica failed..."). I then tried to raise the functional level in "Active Directory Domains and Trusts" on the old server, but it said, "This domain is operating at the highest possible functional level."

Is there any possible way to migrate from Windows Server 2012 R2 to Windows Server 2025?

Thank you for your advice.

Answer 1

Hello SeP,

Thank you for posting in Q&A forum.

Please check the forest functional level and domain functional level by running commands below:

(Get-ADForest).ForestMode

(Get-ADDomain).DomainMode

If it is not Windows Server 2016 or higher, you should demote the 2025 Domain Controller to member server and upgrade the forest functional level and domain schema on the old server (Windows Server 2012 R2).

The domain function level can only be upgraded on the PDC simulation simulator operation host;

Forest functional levels can only be upgraded on schema operations hosts.

Open AD domain and trusts to raise forest functional level.

Open AD Users and Computers to raise domain functional level.

I hope the information above is helpful.

If you have any questions or concerns, please feel free to let us know.

Best Regards,

Daisy Zhou

============================================

If the Answer is helpful, please click "Accept Answer" and upvote it.

Answer 2

Windows server 2025 does not support functional levels older than 2016. Your current 2012 R2 does not support anything newer that level 2012. The only path forward is to install windows server 2019, decommission the 2012 R2 server, raise the functional level to 2019 and then proceed with spinning up the 2025 server, promote it to a DC, decommission the 2019 server and raise functional level again. It's also a VERY bad idea to only have one DC.

Answer 3

Thank you for answers. So you think there will be no problem with demote Windows Server 2025 to same level like older server Windows Server 2012 R2? After this demote Window Server 2012 R2 as domain controller and trash it. After all this. Promote Windows Server 2025 back ? If I understand it ? Thank you