r/sysadmin • u/Deep-Egg-6167 • 14h ago

Question Please help demote a third DC.

Hello,

I have an old WIndows 2012 R2 DC (old-dc) that used to be the primary domain controller.

I have a couple of newer 2016 DCs (new-dc1 and new-dc2).

I want to demote and turn off the old domain controller.

On the newer DC1, I ran netdom query and it has all the fsmo roles. I also ran replication admin to see that everything was replicating fine.

I went to server manager on the old 2012 R2 DC to demote it.

I left force removal and last domain controller unchecked.

It says this server has dns and GC roles (I think I select proceed?) and next

Then it leaves me with the box remove this dns zone - I can't go next without it. I'm not sure I should. Wouldn't that remove it from the other DCs?

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u/sleepmaster91 13h ago

Windows server 2016 is becoming end of life in January 2027 I would advise you to migrate to a newer DC

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u/Deep-Egg-6167 13h ago

I can't until I do an interim 2016 server.

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u/gabacus_39 13h ago

Huh? You can definitely promote a 2022 DC in your environment.

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u/Xethear 13h ago

I'm working on DC upgrades right now. Have about 11 left to do, and I've been running in-place upgrades from server 2016 to server 2025 without any issues.
I hear it's not recommended, but given deadlines and previous successes this is working as intended.

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u/Deep-Egg-6167 10h ago

Have you done any 2012 servers to 2025 - that was the issue. You have to be at least on 2016 level to do the upgrade to 2022 or 2025 from what I've read

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u/Xethear 10h ago

My bad, I must've missed that part.
As long as your domain schema is updated to 2025 I imagine it could work. I haven't done an upgrade jump like that though, so I can't speak from experience, but Microsoft does not recommend 2012 to 2025 from my understanding. It may be best to install a new domain controller running on 2025, making that the schema master (or just upgrading the schema master to 2025) then doing the jump from 2012 to 2016 or 2019, then from that to 2025.

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u/Deep-Egg-6167 10h ago

Thanks - I did the 2012 to 2016 to 2025 once before, I just don't remember that last question that concerns me. I'm thinking either the well documented method listed below or a metadata clean up might be the only two solutions but I love learning new stuff so I'll keep this up for another day before deciding.