I have a Windows 2008 SBS and a Windows 2008 R2 server in the same site in AD despite that fact they are geographically separate and have different IP subnets. In fact they are connected by an IPSEC VPN.
Each is a GC.
This has worked fine for several years but now we need to differentiate between the two for DFS to work properly with Group Policy.
Created and associated subnets for each within AD Sites & Services. Created the two sites and then attempted to move the W2008 R2 server to the new site - get "Access Denied" error....