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Domain Functional Level

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3 replies to this topic

#1 JimFFlagg


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Posted 29 July 2015 - 12:57 PM

I currently have one domain that is a 2003 functional level with 3 x Windows Server 2008 servers (Web Server, Database Server/DC and File Server) for our main office and one Windows 2003 server in our Tucson office. The original domain had a 2000 server so it was originally 2000 mixed functional level but I updated it to 2003 before installing the 2008 servers.


The problem is that I am building a brand new server to replace the old Windows Server 2003 server in Tucson because of the end-of-life thing. I am trying to install Windows Server 2012 but it failed the validation because the Forest is still set to 2000 mixed. I am going to update the Forest after hours tonight but I was wondering if there are any pitfalls I need to look out for before I do it?


Thanks for any input.

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#2 x64


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Posted 29 July 2015 - 02:17 PM

If you are only updating the forest functional level then I do not see any issues. If you have more than one DC (from the above, I get the impression that you don't) then ensure that AD fully fully replicates afterwards before making any other fundamental change to the structure of the domain.


If you are planning to install a 2012 DC then be aware that the the domain controller installation procedure runs the equivalent of forest prep and domain prep silently as part of the first 2012 DC installation. That does extend the schema of AD, so just to be on the safe side ensure that your backups are up to date and to a sufficient standard. However I've never had an issue with AD schema extensions.



#3 Jtiger360


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Posted 17 August 2015 - 12:42 AM

You can only function at the lowest level of your DCs.


Update: Ah misread: I am still in MCSE training, no idea sorry :(


A+ Certified 


MCSE (in-training)

Edited by Jtiger360, 17 August 2015 - 12:45 AM.

#4 sflatechguy


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Posted 23 August 2015 - 01:25 PM

Forest functional level sets the floor for your DCs forest-wide -- so if it's set to 2003, you can't have any Windows 2000 domain controllers in your environment, only 2003 or newer. Note that this doesn't apply to servers, only domain controllers. You can install DCs with more recent versions -- but not all the features offered by those versions will be available until you raise the forest functional level. If the 2000 DC has been decommissioned, and removed properly, you shouldn't have any issues.


However, you said you had already raised the functional level, yet the forest is still set to 2000 mixed. Was it the forest level you raised, or the domain level?

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