I will soon be running adprep32.exe on a Windows 2000 Server, which is the FSMO DC in the network. I am adding two Windows 2008 R2 servers to become the DCs. The first run is 'adprep32 /forestprep'. Then I read this: '...allow the changes to replicate throughout the forest before you prepare any domains', which refers to the next step 'adprep32 /domainprep /gpprep'.
What's the best way to know when the changes are finished replicating throughout the forest? It's a small, in-house, local network. So, I'm assuming it will be within minutes and not some overnight wait.