2003R2 to 2008R2 AD upgrade

My question is two fold.  First is it possible to leave roles such as DHCP and DNS on a dcpromo'd out 2003 server and use only 2008 R2 servers as DCs?  In other words, while in the process of upgrading, can we raise the domain functional level to 2008R2 while those functions...DHCP, DNS are still running on old 2003 Servers that are no longer DC's.

Part 2 - If that is not possible, is it best to split the scope temporarily between the old dc and the new 2008R2 dc before migrating with the Windows Server Migration Tools or just attempt the migration overnight?

Thanks in advance for any advise.
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Joseph DalyCommented:
What I would do is run the adprep for 2008 domain controllers on your domain. After this has been run you can install your first 2008 domain controller. At this point you can still have 2003 and 2008 controller running together.

Depending on how you have your DNS configured it should automatically replicate to the 2008 DC. At this point you can choose to demote the old 2003 DC which should remove the DNS server role.

You can run DHCP on a server that is not a domain controller without issue. If this is easier for you then you can simply leave it on the 2003 server.

You only really have to worry about removing all of the 2003 DCs once you rasie the function level before that 2003 and 2008 DCs can coexist.
habs1994Author Commented:
Thanks for the input.

I have the 2008R2 server installed and replicating DNS OK.  

DHCP is running on the 2003 Server that at one time held all the FSMO roles (now held on the 2008R2 server) and is the first dc in the domain.  It's IP is used heavily for DNS throughout the network so I would like to leave that for the time being but can't you dcpromo that server out and still leave DNS?  

I would also manually change the bridgehead server for Sites to the new 2008R2 server if necessary. All sites point to this main site for replication and the old 2003 server is the bridghead.

I have found documentation that shows a quick DHCP migration scheme using netsh instead of the migration tools.

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habs1994Author Commented:
THis answers my questions regarding DNS but I am also looking for DHCP tips
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