How to merge 2 Domain Controllers of the same Domain that has been separated for a long period?

Question

Hi, I have a setup with 2 domain controllers for the same domain (PriDC and SecDC). PriDC was installed and had users and computers added to it. PriDC is located in SiteA. I will install SecDC, a few months after PriDC, in a different location, SiteB. My idea is to take an image from PriDC and load it in a temp server in SiteB. After that, I will install SecDC and join as Domain Controller to this Domain. Consider that I have to create other users and join other computers to this Domain Controller (SecDC) in SiteB. I need to have both Domain Controllers running on the same site (SiteA). My question is: Is it possible to merge both Domain Controllers (PriDC and SecDC) whitout loose any information or object? Will they synchronize? Thanks.

Answer 1

Hi Daniel,

Thanks for your question here on Q&A.

Why take a clone of PriDC to SecDC, as when if you install DC services on SecDC (clean) and join that DC to the domain/install DC services - all the data from PriDC (the primary DC in the domin) is cloned over to SecDC in the process?

I will recommend that ay :)

See here: https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/install-active-directory-domain-services--level-100-#BKMK_GUI

"On the Deployment Configuration page, choose one of the following options:

• If you are installing an additional domain controller in an existing domain, click Add a domain controller to an existing domain, and type the name of the domain (for example, emea.corp.contoso.com) or click Select... to choose a domain, and credentials (for example, specify an account that is a member of the Domain Admins group) and then click Next."

Else let me hear

Answer 2

Hello Daniel Dias, Thank you for posting in Q&A forum. Based on your description, you want to clone the PriDC, load it on the temporary server of sitB, and then do a clean install of the SecDC on sitB and join it to the temporary server. Regarding your question, my advice is not to clone PriDC. Here are my recommendations:

1. It is not recommended to clone PriDC: It is not recommended to clone domain controllers as duplicate SIDs, USNs, and other issues may occur.
2. Install SecDC directly on PlantB: Perform a clean install of Windows sever on the server that will be the SecDC. Then add the ADDS role and promote the server to a domain controller. During the upgrade process, select the option to add domain controllers to an existing domain. 3.AD Data Replication: Once a SecDC is promoted to a domain controller, it automatically replicates data from the PriDC. Make sure that the two domain controllers can communicate with each other and that the necessary ports are open.
3. Create a user and join a domain: You can create a new user account and join the computer to a domain in PlantB. These changes will also be replicated to PlantA's PriDC.
4. Transfer of all nodes of Plant B to Plant A: When you are ready to transfer everything to PlantA, make sure that the domain controllers are already synchronized. You can use repadmin /showrepl >C:rep1.txt to check the AD replication status and DCDIAG /v to check the running status of the DC.

Tip: By default, all the Domain Controllers in the same domain (even if they are in different site) will replicate with each other). I hope the information above is helpful. If you have any question or concern, please feel free to let us know. Best Regards, Daisy Zhou

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