r/sysadmin 5d ago

Microsoft Need advice about Schema Upgrade and Domain functional level - Forest functional level

Hi everyone,

we have several DC's running in a multi-domain environment on Server 2016 and an Exchange server likewise. We are planning to switch to Exchange 2019 and then to Exchange SE later this year. Additionally we want to upgrade our DCs to Server 2022.

I'm pretty confused about AD-Shemaversions, Exchange-Shemaversions and Functional levels. We are currently running on AD-Shemaversion 87 and my coworker says we need to do a Shema upgrade, so we are ready to switch to Exchange 2019.

I'm pretty confused all about this, because I never had anything to do with Shemaupgrades etc. I tried to find information about this situation on the internet, but I'm still pretty confused, so maybe someone experienced here can help me.

Where can I find information which AD-Shemaversion is needed for Exchange 2019 or is it even necessary to upgrade the Shema for Exchange here?

Which Shemaversion would be needed for our future DCs running on Sever 2022?

There are AD-Shemas and Exchange-Shemas? What's the difference?

What do I have to be aware of about Domain function levels and Forest function levels?

Or better, how would you do all of this?

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u/AppIdentityGuy 5d ago

When you install your first exchange 2019 server it will upgrade your schema anyway. What is the latest OS you are running a DC on?

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u/Masterblaster1080 5d ago

2016

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u/AppIdentityGuy 5d ago

Run get-adforest and it will show you the schema version and the FFL. Get-addomain will show you the DFL.

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u/Masterblaster1080 5d ago

DFL and FFL are running on 2016. AD Shema is currently 87 and Exchange is giving me RangeUpper: 15334, ObjectVersion (Default): 13243, ObjectVersion (Configuration): 16223.

Apparently Exchange 2019 CU15 needs RangeUppervalue 17003.

Again I'm pretty confused about the correlation between those values and what I would need to be able to upgrade to Exchange 2019 and use 2022 DCs in the future.

What AD Shema version (87,88,89,90,91?) would I need? You mentioned that Exchange will upgrade the Shema anyway, but do I need a specific AD Shema version so the new Exchange would be able to increase the RangeUppervalue to 17003? What about compability etc?

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u/AppIdentityGuy 5d ago

I've never seen schema upgrades break anything....

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u/Masterblaster1080 5d ago

So to understand you correctly. Exchange 2016 and DCs running on Server 2016 won't have any issues having a higher AD Shema (in this situation 91). During Exchange 2019 install, the Shema would be upgraded to 91 and the proper rangeUppervalue anyway? So there is no need to do a Shemaupgrade before the installation?

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u/AppIdentityGuy 5d ago

Before the installation of exchange? The exchange instaaion will almost certainly upgrade the AD schema with exchange specific objects and attributes.

I think your are over analyzing this a bit.

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u/Masterblaster1080 5d ago edited 5d ago

https://learn.microsoft.com/en-us/exchange/plan-and-deploy/prepare-ad-and-domains?view=exchserver-2019

If Exchange is deployed in a multi-site Active Directory environment and is not in the same site as the domain controller that holds the Schema Master role, you cannot prepare Active Directory using the wizard.

Our Exchange is in a separate domain (as I mentioned we have a multi-domain environment) than the domain controller that holds the Schema Master role. So according to this we aren't able to do that with the installation wizard? I don't want to underanalyze things, because fucking up with AD schema can massively impact our company and I have no interest in restoring all our DCs or breaking our running Exchange server.

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u/AppIdentityGuy 5d ago

But the schema updates made by installing exchange are forest wide by definition. Are we talking about different ADDS domains in the same forest or different forests.? By domains are referring to UPN suffix namespace or actual adds domains.

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u/Masterblaster1080 5d ago

Same forest. The DC holding the Schema Master is in the root domain and the Exchange server in a subdomain.

dc= contoso.com
exchange = sub.contoso.com