question on demoting DCs and azure ad connect

Question

very soon will be moving to 2012 DCs from 2008r2.
once we transfer all the roles, going to switch IPs from the two 2008r2 servers with the new 2012 servers, to keep from having to touch all the devices with static IPs.

once question - do you HAVE to shutdown the old servers after migrating away from them?

reason I am asking, we use 365 in hybrid mode, and have azure ad connect running on one of the 2008 servers.
could we leave it running after demoting it to member server, so we can move azure ad connect later, would prefer to do it few days later.

would rather not make too many changes at one time if possible.

Answer 1

Demotion and leaving as a member server is fine to do. In case the demotion does not go cleanly, you can finish with metadata clean up.
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/ad-ds-metadata-cleanup
https://techcommunity.microsoft.com/t5/itops-talk-blog/step-by-step-manually-removing-a-domain-controller-server/ba-p/280564

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Answer 2

Hi,

once question - do you HAVE to shutdown the old servers after migrating away from them?

Once you complete the migration , the IP switch and remove the service in old servers ( Azure AD connect , Domain controllers), you don't have to shutdown the servers , because the service are already removed on old servers and there is no risk for IP conflict.

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