Final steps to migrate Active Directory to Windows 2012 R2 include the decommission of the first 2008 R2 DC migrating the DHCP to the new Windows Server 2012 R2 .
If the old Domain Controller is acting also as DHCP server, the DHCP role should be migrated to the new server 2012 R2 in order to keep same settings.
Blog series
Migrate Active Directory to Windows 2012 R2 - pt. 1
Migrate Active Directory to Windows 2012 R2 - pt. 2
Migrate Active Directory to Windows 2012 R2 - pt. 3
Export DHCP settings
If your primary old Domain Controller has the DHCP role installed, before the decommission we need to migrate the DHCP configuration to the new 2012 R2 server.
Login to the Windows Server 2012 R2 previously deployed (DC01) and open the PowerShell shell.
Run the following command to export DHCP settings:
Export-DhcpServer –ComputerName server.domain.com -Leases -File path\dhcpconfig.xml -verbose
PS C:\> Export-DhcpServer –ComputerName w2k8r2-dc01.nolabnoparty.local -Leases -File C:\temp\dhcpconfig.xml -verbose
Exit the PowerShell. The exported dhcpconfig.xml file contains the configuration of current DHCP server.
Decommission last 2008 R2 Domain Controller
To decommission the last 2008 R2 Domain Controller, we have to follow the same procedure used in part 1 - Decommission secondary Windows 2008 R2 DC.
From the Windows 2008 R2 Domain Controller run the dcpromo command and follow the steps to demote the server.
Deploy a new 2012 R2 server and promote it as Domain Controller following the same procedure used in part 2 - Deploy the first Windows 2012 R2 DC.
DON'T check the Delete the domain because this server is the last domain controller in the domain option and click Next to proceed.
Click Yes to continue.
Type a Password then click Next.
Click Next to start demoting the Windows 2008 R2 Domain Controller.
The demoting process takes place. The server reboots automatically.
When the server has rebooted, remove demoted DC from the domain.
Check the computer has been disabled in Active Directory.
This server won't be used anymore, shutdown the VM.
If you want to keep same IP address of old Domain Controller, change the IP in the new Windows 2012 R2 Domain Controller. When done, reboot the VM.
When the server has restarted, from Server Manager select Tools > Active Directory Users and Computers. Expand the domain name and select Domain Controllers. In the right pane the new Domain Controller shows up.
To verify the DNS functionality, from Server Manager select Tools > DNS. Expand the server name and Forward Lookup Zones. Right click the domain name and select Properties. Ensure DC is listed in the Name Servers tab.
Import DHCP settings
If your primary Domain Controller has the DHCP role installed, we need to restore the DHCP configuration previously exported from the old 2008 R2 server to keep leases consistency.
Login to the Windows 2012 R2 (DC01) and open the PowerShell shell.
Run the following command to import DHCP settings:
Import-DhcpServer –ComputerName server.domain.com -Leases -File path\dhcpconfig.xml -BackupPath C:\temp\dhcp_backup\ -verbose
PS C:\>Import-DhcpServer -ComputerName w12r2-dc01.nolabnoparty.local -Leases -File C:\temp\dhcpconfig.xml -BackupPath C:\temp\dhcp_backup\ -verbose
Type Y to proceed with import.
The configuration is imported.
Open the DHCP snap-in, right click the server name and select Authorize option.
The imported scope is now active on the new 2012 R2 server.
The migration procedure is complete. Check the Active Directory health status running same script used at the beginning of the migration to be sure no issues are detected.
Troubleshooting
A common issue faced during the migration is the missing SYSVOL and NETLOGON shares in the new 2012 R2 DCs after their promotion.
Check the shares availability using the command:
C:\>net share
To fix this problem is necessary to force an authoritative and non-authoritative synchronization for replicated SYSVOL. Several procedures are available in Internet to guide you through the synchronization process.
When the shares are available again, the migration can be considered completed.
