How to Migrate Domain Controllers to Windows Server 2025 (The Right Way)

Learn how to Upgrade Active Directory to Windows Server 2025 while keeping AD online and minimizing disruption.

In this step-by-step tutorial, we walk through the safe, repeatable process of a staged migration of your Domain Controllers to Windows Server 2025 (health checks → temporary DC → swap DCs → raise functional levels) using Microsoft-recommended practices. We don’t just show you the install; we cover the critical health checks, FSMO role transfers, and the new 32k page database optional feature that modernizes Server 2025 AD performance and scalability.

You’ll learn how to:
✅ Validate AD health before and after the upgrade (DCDiag / Repadmin / DFSR)
✅ Add a temporary DC (2016/2019/2022) to keep the domain stable during the transition
✅ Demote legacy DCs and promote Windows Server 2025 DCs cleanly
✅ Transfer FSMO roles safely and keep DC hostnames + IPs intact
✅ Raise Domain + Forest Functional Levels to Windows Server 2025 (the right prerequisites)
✅ Enable the 32k page database optional feature

Why this method: Microsoft’s recommended path is to promote new DCs on the newer OS and demote the old DCs, rather than relying on in-place upgrades.

By the end of this guide, you’ll have a fully upgraded Active Directory environment running on Windows Server 2025 — while keeping domain controller hostnames and IPs intact.

#WindowsServer2025 #ActiveDirectory #DomainController #ServerUpgrade
Applies to:
✅ Windows Server 2025
✅ Windows Server 2022
✅ Windows Server 2019
✅ Windows Server 2016
✅ Windows Server 2012 R2
Chapters:
0:00 Introduction
0:42 Environment and Key Requirements
2:03 Upgrade Process Overview
4:17 Check Domain and Forest Health
6:04 Promote Temporary Domain Controller, DC03
8:33 Update DHCP Options and Static IP Assignments
9:51 Demote Domain Controller, DC02
12:10 Promote New Domain Controller, DC02
14:37 Demote Last Legacy DC
15:28 Upgrade Domain and Forest Functional Levels, 2016
16:33 Promote Windows Server 2025 to Domain Controller, DC01
18:18 Demote/Promote Domain Controllers, DC02 and DC03
19:12 Upgrade Domain and Forest Functional Levels, 2025
20:37 Demote and Remove from the Domain, DC03
20:58 Enable 32k Page Database for Active Directory
21:52 Cautions, Considerations, and Compliance
23:35 Thank you for watching
23:58 Links
Glossary:
ADDS = Active Directory Domain Services
DCDiag = A command-line tool used to run a series of tests on a domain controller
DFSR = Distributed File System Replication
DNS = Domain Name System
FSMO = Flexible Single Master Operations
GC = Global Catalog
Repadmin = A diagnostic tool used to monitor and troubleshoot replication between domain controllers
GitHub:
https://github.com/DariensTips

Commands:
https://github.com/DariensTips/Upgrade-Active-Directory-to-Windows-Server-2025/blob/main/UPGAD2025_Commands_20250918.ps1
Links & Resources:
https://learn.microsoft.com/en-us/powershell/module/addsdeployment/uninstall-addsdomaincontroller
https://learn.microsoft.com/en-us/troubleshoot/windows-server/active-directory/fsmo-roles
https://learn.microsoft.com/en-us/troubleshoot/windows-server/group-policy/force-authoritative-non-authoritative-synchronization
https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/troubleshoot-missing-sysvol-and-netlogon-shares
https://learn.microsoft.com/en-us/windows-server/get-started/upgrade-conversion-options
https://learn.microsoft.com/en-us/windows-server/get-started/upgrade-migrate-roles-features
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/active-directory-functional-levels
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/demoting-domain-controllers-and-domains--level-200-
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/find-active-directory-schema
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/upgrade-domain-controllers
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/enable-32k-pages-optional-feature
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/plan/raise-domain-forest-functional-levels
https://learn.microsoft.com/en-us/windows/release-health/windows-server-release-info
Related videos and Playlists:
https://www.youtube.com/playlist?list=PLLmyrX1SggDDM1qWicJm6i_rS1euzUjcP
https://www.youtube.com/playlist?list=PLLmyrX1SggDDcpBDqkEsf8iGh6RaPAyI0
Attribution:
https://www.vecteezy.com/free-videos/
https://www.vecteezy.com/video/2043222-many-fireworks-in-event-amazing-with-black-background

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