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Solved: How do I re-run Forest Prep to fix verification of replica failed problem when joining new DC

By: Author Alex Lim

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Home > Solved: How do I re-run Forest Prep to fix verification of replica failed problem when joining new DC

Question

I am currently working on migrating from Windows Server 2012 R2 as the Domain Controller to Windows Server 2019. Both Windows Server OS running on VMware ESXi 7.0. When I try to add the Windows Server 2019 as domain controller, below error message display:

Verification of replica failed. The forest functional level is not supported. To install a Windows Server 2019 domain or domain controller, the forest functional level must be Windows Server 2008 or higher.

Verification of replica failed. The forest functional level is not supported. To install a Windows Server 2019 domain or domain controller, the forest functional level must be Windows Server 2008 or higher.

I have executed the command Get-ADForest on the Windows Server 2012 R2 domain controller, and the output for ForestMode is Windows2003Forest.

I have inserted the Windows Server 2012 R2 ISO into the virtual drive to execute ADprep /forestprep command, but I got a message:

Forest-wide information has already been updated
Adprep did not attempt to rerun this operation.

Forest-wide information has already been updated. Adprep did not attempt to rerun this operation.

How do I force the Forest Prep to rerun?

Solution

If you have a Windows Server 2012 R2 Domain Controller, then the Forest Prep and Domain Prep have already been done for Windows Server 2012 R2. If you have no Windows Server 2003 domain controllers, you can raise the domain and forest functional levels.

Step 1: Update the forest and domain functional levels as high as it will let you.

Step 2: Migrate SYSVOL replication from FRS to DFSR.

Step 3: Add a Windows Server 2019 DC as a domain controller.

Reference

Windows Server > Storage at Microsoft > Streamlined Migration of FRS to DFSR SYSVOL

Alex Lim is a certified IT Technical Support Architect with over 15 years of experience in designing, implementing, and troubleshooting complex IT systems and networks. He has worked for leading IT companies, such as Microsoft, IBM, and Cisco, providing technical support and solutions to clients across various industries and sectors. Alex has a bachelor’s degree in computer science from the National University of Singapore and a master’s degree in information security from the Massachusetts Institute of Technology. He is also the author of several best-selling books on IT technical support, such as The IT Technical Support Handbook and Troubleshooting IT Systems and Networks. Alex lives in Bandar, Johore, Malaysia with his wife and two chilrdren. You can reach him at [email protected] or follow him on Website | Twitter | Facebook

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