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I have a Windows 2008 SP2 server running as a primary domain controller with active directory, file shares, DHCP, DNS, and MS SQL 2008. I plan on upgrading to 2008 R2 (with the same SKU) to take advantage of some of the new features included in this release.

If I just pop in the CD in and run through the upgrade process, will active directory's functional level remain at the 2008 level, or will it be upgraded to 2008 R2?

I have a mixed environment of XP, Vista, and Windows 7 workstations. Are there any other considerations I should be aware of or prepare for?

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up vote 4 down vote accepted

The domain functional level is never automatically elevated, it must be manually initiated. This is because it is the administrator's responsibility to ensure all the domain controllers can support that functional level and any prerequisite configuration activities (e.g. adprep) have been completed.

With that said, if you have more than one domain controller, I think it is best practice to first dcpromo the controller to remove it from domain controller responsibilities before you upgrade it to the new version. Since I'm paranoid, I like to do clean DC installs, versus upgrades, in order to mitigate risk.

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There's just the one DC right now. I have a second server I had intended to use as a second DC, so I can put it to use here. If I set up that second server as 2008 R2 and attach it to the domain as a DC at the 2008 functional level, migrate everything, then disconnect theh original server and do a "adprep /forrestprep" on the new server, would that be the process you would take? – Force Flow Apr 18 '12 at 12:49
That would be what I would recommend. If you're a control freak (like me), I would manually move all of the FSMO roles to the new server before you demote the old server. I know dcpromo is supposed to do this for you, but I personally prefer doing those things myself. I think there is also a adprep /domainprep that you'll need to do as well... TechNet has some good articles on AD migration at: and – newmanth Apr 18 '12 at 13:32

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