Upon restoring a domain controller to a new or isolated network in example a DR environment, the domain controller will lose access to its other domain controllers for replication. You might find you cannot start the DNS server and or Active directory services.
To force the server to start without checking for others modify the below key and reboot the server
Add the Following reg Key
Value name: Repl Perform Initial Synchronizations
Value type: REG_DWORD
Value data: 0
You should then go into Active Directory Sites and services and remove the old Domain Controllers and Also go into the DNS server and remove any references in the Nameserver tabs for the Zones
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