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I am &nbsp;in the process of upgrading our network from 2008 to 2012. <br />
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I have 2 DC's at each site and all are running DNS as well. I have started demoting the current DC's to member servers( &nbsp;1 at a time) and will be removing from AD. &nbsp;Dcpromo has worked fine and I have had no errors.<br />
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My 1st question is do I need to do any other cleanup in AD before I build the new DC's under 2012 as I mentioned I will be completely removing the old servers but I want to use the <b>same names </b> for the new DC's as the old one(s). &nbsp;Also they were all DNS servers so a similar question would be do I need to do any cleanup in DNS in order to add the new DC's with the same name(s).
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I am  in the process of upgrading our network from 2008 to 2012. 

I have 2 DC's at each site and all are running DNS as well. I have started demoting the current DC's to member servers(  1 at a time) and will be removing from AD.  Dcpromo has worked fine and I have had no errors.

My 1st question is do I need to do any other cleanup in AD before I build the new DC's under 2012 as I mentioned I will be completely removing the old servers but I want to use the same names  for the new DC's as the old one(s).  Also they were all DNS servers so a similar question would be do I need to do any cleanup in DNS in order to add the new DC's with the same name(s).

migrating 2008R2 DC to 2012 DC

Windows Server 2008 and Windows Server 2008 R2, based on the Microsoft Vista codebase, is the last 32-bit server operating system released by Microsoft. It has a number of versions, including including Foundation, Standard, Enterprise, Datacenter, Web, HPC Server, Itanium and Storage; new features included server core installation and Hyper-V.

Windows Server 2008

Windows Server 2012 is the server version of Windows 8 and the successor to Windows Server 2008 R2. Windows Server 2012 is the first version of Windows Server to have no support for Itanium-based computers since Windows NT 4.0. Windows Server 2012, now in its second release (Windows Server 2012 Release 2) includes Foundation, Essentials, Standard and Datacenter, and does not support IA-32 or IA-64 processors.

Windows Server 2012

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.