Uit:
Technologies for Federating Multiple ForestsBefore you can create a forest trust, you need to verify that all domain controllers in both forests are running Windows Server 2003. You also need to verify that you have the correct Domain Name System (DNS) infrastructure in place and that you have established the appropriate functionality level for Active Directory. This means that the forest has to be raised to the Windows Server 2003 functional level and you cannot add any more Windows 2000 or Windows NT Server 4.0 domain controllers to the forest.
2003 functional level is dus voldoende, zoals mijn voorganger al correct riep.
MCSE NT4/2K/2K3, MCTS, MCITP, CCA, CCEA, CCEE, CCIA, CCNA, CCDA, CCNP, CCDP, VCP, CEH + zwemdiploma A & B