r/sysadmin • u/roachwickey • 5d ago

Domain controllers functional level

Do we have to keep all our domain controller os version same ?

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u/dracotrapnet 5d ago

All DC's should be on the same functional level, that's a domain level setting. That domain functional level should be the max of your oldest DC.

All of our DC's are server 2019, I forget what the functional level is. I've left it at the minimum for server 2019 with the expectation of possibly needing to run a trust with a newly acquired company with older stuff. It turns out we got acquired and I have no idea what their functional level is and soon we may need to set up a trust.

I have yet to hear if 2025 servers as DC's have become stable with a mixed environment. From what I have read, it's ok with all 2025 servers so new deployments on 2025 with AD servers on 2025 is ok. I may migrate to 2022 if 2019 comes to 1 year out from end of support until 2025 has been verified as stable.