We have 4 domain controllers that run Windows Server 2008 R2. These have been introduced a while back and there are no other DC's that run a lower OS.
The domain functional level is running at Windows Server 2003 and the forest functional level at Windows 2000 (only one domain in the forest).
What order do I need to upgrade the forest/domain functional level in? Do I need to do the forest level first - to 2003, then to 2008 then to 2008R2. Or can I go straight to 2008 R2?
Do I raise the domain functional level straight after? Again to 2008 first, then to 2008 R2? Is there a specific order?
Anything I need to be concerned about or can I pretty much just do this on the fly?