we are migrating our AD forest. now,we have only server 2008 and 2012 R2 DCs,but we do have 2000 and 2003 member servers. can we still upgrade to 2008 R2 domain-forest functional level first as a first step? once we have all 2012 R2 DCs,we will then upgrade there too.
what are the (security) benefits by running on 2012 R2 domain-forest functional level?