Merging multiiple domains with the same existing domain name (office.local)

active-directorydomain-controllerwindows-server-2008windows-server-2012

I am working with a new client who has 5 offices and four of which have a single domain controller with the name of OFFICE.LOCAL and another one with the domain controller DENTAL.LOCAL. Oh and all of the servers are named SERVER as well.

My goal would be to have all locations under the same forest (as shown below) and make each location’s server a member server under a Primary Domain Controller.

COMPANY.com
-DivisionNameA.corp.com
-DivisionNameB.corp.com
-DivisionNameC.corp.com
-DivisionNameD.crop.com
-DivisionNameE.corp.com

My thought is that I would need to do the following:

  1. Rename the domain of the site that houses the new Primary Domain Controller (DC) to ad.corp.com.
  2. Rename all of the other remote domains to have unique domains such as DivisionNameA.local
  3. Create a trust between ad.corp.com and all of the remote domains
  4. Use ADMT to migrate all of the domain objects from each of the remote domains to ad.corp.com.
  5. Demote each of the remote DCs.

My Questions:

  1. Am I going about this the right way? Or is there a better way?
  2. By doing this would I then have to rejoin all of the workstations (20+ per location) to the new DC?
  3. Is there a way to do this without having to rejoin all of the workstations to the new DC?

Best Answer

Honestly, 100 computers (five locations with 20+ each) really aren't very many. You could write a script in batch or powershell to add them to the new domain remotely. (PowerShell 3's version of add-computer allows you to add a remote computer to the domain.)

No, the part that makes me nervous is the five identically named DCs in identically named domains.

I suspect that what's involved is:

  1. Setting up a brand new domain (ad.example.com).
  2. Picking a branch (start with the smallest or nearest?) and migrating the users and computers using a script, ADMT, powershell, or a third party tool. (I found a bunch of hits for this. Here's a couple.)
  3. Demoting and renaming the old DC, then joining it to the new domain and promoting it to be a local DC in the new domain (so you can have a DC at each branch).
  4. Repeat steps 2 and 3 for the other branches, one at a time.

In other words, I would personally skip the renaming of the original domains and instead fold them into the new domain one by one, in sequence.

You haven't mentioned a test environment, but I would strongly suggest testing this thoroughly against an environment with dummy accounts and computers. Hiring an expert might also be a good idea.

Good luck!

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