Step-By-Step: Downgrading A Windows Server Domain and Forest Functional Level


Once upon a time, it was not possible to downgrade Windows Server forest and domain functional levels once upgraded. Enter Windows Server 2012 R2 and it's Active Directory enhancements, as detailed by the video below, backed by PowerShell automation capabilities. This enablement makes the forest and domain functional level downgrade even easier. Do keep in mind however that the lowest functional level that can be utilized is Windows Server 2008 R2.

In this Step-By-Step, we will be using a domain controller with forest and domain function level set to windows 2012 R2. PowerShell will be utilized as there is no GUI to perform this downgrade.

Lets get started.

  1. Log o to the domain controller as domain admin / Enterprise admin.
     
  2. Run PowerShell with Admin rights.
     
     
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  3. In PowerShell type Import-Module -Name ActiveDirectory To import the AD module. 

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  4. Confirm the forest and domain function levels by typing the following in PowerShell: 
     
    (Get-ADForest).ForestMode
     
    (Get-ADForest).DomainMode
     
     
  5. Next to set the forest function level to windows server 2008, in PowerShell type:
     
    Set-ADForestMode –Identity “CANITPRO.com” –ForestMode Windows2008Forest
     
    NOTE: 
    In this example the FQDN is CANITPRO.com which can be replaced with your desired domain name.
     
     
  6. Enter Y to confirm the change
     

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  7. Next to downgrade the domain function level to windows server 2008, in PowerShell type:
     
    Set-ADDomainMode –Identity “CANITPRO.com” –DomainMode Windows2008Domain
     
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  8. Confirm the new forest and domain function levels have been downgraded by typing the following in PowerShell: 
     
    (Get-ADForest).ForestMode
     
    (Get-ADForest).DomainMode
     
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