Can a 2003 server act as a Backup Domain Controller to a 2012 server? Can a 2012 server be a Backup domain controller to a 2003 server?

I'm adding this server and it will have some miscellaneous software installed that I'd like to install and make functional before making this the Domain controller and transferring FMSO, DHCP, DNS, Sophos control panel, QuickBooks server manager, Kyocera plotter/scanner. The reason for this is so that if something goes awry, I would still have the 2003 server performing all these roles.

Is it possible to add the Active Directory Domain Services role without the machine needing to become the PDC immediately?
Is it possible to use a 2003 server as a BDC to a 2012 server?
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You cannot have a 2003 DC and a 2012 DC within the same domain. You can have the servers on the same domain, but the 2003 would have to be demoted.

Please mark as "Answered" if this helps.
Yes, you can.  The domain and forest functional levels have to be at 2003 level.  There was an issue with having both a 2012 R2 DC and 2003 DC, but there is a hotfix available.
Lee W, MVPTechnology and Business Process AdvisorCommented:
The answer is no because the terms and concepts you're talking about don't apply to Active Directory.

There is no such thing as a BDC and no PDC in terms of a "primary" - there are FSMO roles.

Active Directory uses roles - 5 different ones - FSMO roles.  These can be split or remain on a single server.  Further, a BDC - in NT4 - the last time that term applied was NOT writable - it was a read-only copy of the directory - in Active Directory, EVERY DC is a read/write copy

So, what can you do?  Yes, if you leave your domain and forest functional levels at 2003, you can - FOR NOW - leave the 2003 server running as a DC.  UNFORTUNATELY, this would be VERY unwise.  Why?  2003 is no longer supported.  While it may work TODAY, Microsoft is no longer testing patches and updates that for 2012 to ensure they don't affect compatibility with 2003.  While it may work today, it could break tomorrow.  Further, the fact that newly discovered exploits are not being fixed in 2003 means keeping a 2003 server on the network increases your likelihood of being hacked on a daily basis.

If you want a second server, get a second server with an operating system that is still supported.

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:)  I've given up on correcting people whenever they refer to a PDC and BDC...
@footech - Agreed but Lee is correct, the PDC/BDC identity has no real meaning in Active Directory (these are hold over identities from Windows NT 4).

@bwierzbicki - In Active Directory all DC's are considered to be equal (or partners).

As Lee and footech have both stated.  So long as your current Forest and Domain Functional Levels allow for it, then you *can* have both 2003 and 2012 DC's running side by side.

Understanding Active Directory Domain Services (AD DS) Functional Levels

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Windows Server 2012

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