Does forest functional and domain functional levels have bearing on tust relationsships? Can I have a 2008 forest at 2008 level and 2003 forest at 2003 level and have forest trust between them? Or is it better to leave all DCs at 2003 until I am done with 2003 forest? Thanks

Change of Forest Functional Level does not affect any external trusts. With out any worries you can raise Functional Level of domain. External trust will work as usual. Rather than this with forest functional level windows 2003, you will get many new features…. http://www.petri.co.il/understanding_function_levels_in_windows_2003_ad.htm http://technet.microsoft.com/en-us/library/cc738670(WS.10).aspx Check Similar threads Forest Functional Level change and affect on current trust relationships http://social.technet.microsoft.com/Forums/en-US/winserverDS/thread/b398b627-6b91-4cb7-af1a-80c944514fe6