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Can windows 2000 and windows 2003 domain controllers coexist?

Dear Experts:
We need to upgrade our existing windows 2000 active directory structure to windows 2003 active directory.  There are two windows 2000 domain controllers in our small network.
We will install a windows 2003 member server into our existing win2k AD and promo it as domain controller.  At this point, which domain our users are connected when they log into our domain?  Are they connected to the old win2k Active Directory or this new win2003 active directory?
How do we know if they are connected to the new win2003 DC or our old win2k DC?
Can they still connect to our existing exchange 2003 server(member server)?
Thanks,
Charlie
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Jon BrelieSystem Architect
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Commented:
Your new 2003 controller will function in tandem with the 2000 controllers.  You will need to transfer the FSMO roles to the 2003 controller and eliminate the 2000 controllers before you can raise the domain functional level.
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Top Expert 2012

Commented:
You can have both DCs running within the same domain both will be working together just like if they were both 2003 or 2000 DCs.

Author

Commented:
1) If I don't transfer the FSMO roles, does that mean that our users can still log into our existing windows 2000 domain and exchange 2003 server like before.  Users will not see any differences.

2) If (1) is true, this approach we do the upgrade  to 2003 AD is very safe.  Because we can just demote this new windows 2003 DC and fall back to our old windows 2000 Active Directory if something happens when we promote this new windows 2003 Domain Controller.


Thanks
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Top Expert 2012
Commented:
Correct the users will not see a difference at all.

You can demote the old server as well if there is a problem
Jon BrelieSystem Architect
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Commented:
Yes, you won't need to do anything more to keep all three servers working in tandem.

However you will need to transfer those roles to the 2003 server and demote your 2000 servers before you can raise the domain to 2003 functional level.  This is not required, however, and can be done at a later date.

Author

Commented:
Great comments!

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