What happens to Windows Server 2012 Domain Controller when we Upgrade Domain & Forest Functional Level to Migrate to Windwos Server 2019

Question

Dear Community,

I want to migrate Windows Server 2019 Active Directory Role to Windows Server 2019 Server. What happens to Windows Server 2012 Domain Controller when we upgrade Domain & Forest Functional Level to Windwos Server 2019 as its pre-requisite to upgarde to Widnwos Server 2019 Domain Controller.

Will my windows Server 2012 DC will keep running after I upgarde the Domain & Functional Level to 2012?

Kindly help me out in this regard.

Answer 1

I'd just do them one at a time and confirm health is good in between doing them. Since you have multiple domain controllers you can take the old ones off line either before or after as needed. Having 2012 and 2019 domain controllers side by side long term is not a problem.

. --please don't forget to Accept as answer if the reply is helpful--

Answer 2

Hi,
For your questions:
If you want to keep your 2012 DCs in the domain, the function level can't be raised to 2016.
If you want to raise the function level to 2016 , the 2012 DCs must be demoted (after the new DC was added) .

To add the 2019 DCS:

The minimum requirements to add a Windows Server 2019 Domain Controller is a Windows Server 2008 functional level. The domain also has to use DFS-R as the engine to replicate SYSVOL.

Since you have 2012 DCs in the domain, make sure the fonctional is 2012 (or raise it to 2012 ), and confirm the DFSR is used for the sysvol replicaiton.
You can confirm the DFSR is used by the command dfsrmig.exe /getglobalstate
If the Result: 3 (ELIMINATED) the DFSR is used for the replication.
If not, FRS should be migrated to DFSR:
https://learn.microsoft.com/en-us/windows-server/storage/dfs-replication/migrate-sysvol-to-dfsr

After the 2 requirements meet, , we should also make sure everything is working well, following command for your reference :
Dcdiag /v >c:\dcdiag1.log
Repadmin /showrepl >C:\repl.txt
Repadmin /showreps * 

Then the new DC can be added , following for your reference:
https://www.petenetlive.com/KB/Article/0001262(third-party link)

Last, you can consider to keep the old DC or raise the functional level.

This response contains a third-party link. We provide this link for easy reference. Microsoft cannot guarantee the validity of any information and content in this link.

Best Regards,

Answer 3

2012 domain controllers will be fine.

The two prerequisites to introducing the first 2019 domain controller are that domain functional level needs to be 2008 or higher and older sysvol FRS replication needs to have been migrated to DFSR
https://techcommunity.microsoft.com/t5/Storage-at-Microsoft/Streamlined-Migration-of-FRS-to-DFSR-SYSVOL/ba-p/425405

I'd use dcdiag / repadmin tools to verify health correcting all errors found before starting any operations. Then stand up the new 2019, patch it fully, license it, join existing domain, add active directory domain services, promote it also making it a GC (recommended), transfer FSMO roles over (optional), transfer pdc emulator role (optional), use dcdiag / repadmin tools to again verify health, when all is good you can decommission / demote old one.

--please don't forget to Accept as answer if the reply is helpful--

Answer 4

what happens to 2012 DCs?

nothing

Will they stop working at that time?

No

want to ask that after upgrading the functional level and setting DFSR to be used for the sysvol replicaiton, Will my 2012 DCs will still be functional.

Yes, see my reply above. --please don't forget to Accept as answer if the reply is helpful--

Answer 5

That's great. One more thing that I want to ask is that once I want to add additional domain controller with Windows Server 2019 , at this stage what will happen to Windows Server 2012?I mean can I keep migrating each 2012 after that or will I have to decomission 2012 as you said:

"when all is good you can decommission / demote old one."

So I have like 4 Domain Controllers one on each site all with Windows Server 2012. So how will I migrate each DC to Windows Server 2019 and what about demoting them?
Like please guide on this.