Doubts regarding Domain and Forest Functional Levels

john_samson · March 2014

Hi Friends, I was going through the 1st chapter of MCSA preparation and read about the Domain and Forest Functional levels. In the book I was following, I read this line- "The functional level of a domain or forest does not affect the operating system that you can use on member servers and workstations that are joined to a domain or forest." The above statement refers to servers or workstations which includes clients as well as Domain Controllers ,isn't it? But when I started reading the details about the different domain functional levels like "Windows 200 Native" ,"Windows Server 2003" and "Windows Server 2008" ,all of them mentions the DC's should run the correct version of Windows Server OS depending on the Domain Func. Levels! For example, Windows Server 2003 can only support DCs running Windows Server 2003 & 2008 but not any earlier versions like Windows 2000 or Windows NT. Then the first statement("The functional level of a domain or forest does not affect the operating system that you can use on member servers and workstations that are joined to a domain or forest.") does contradict the definition of the Domain Functional Levels ,doesn't it? Once it says that you have restrictions in using OS depending on "Functional Levels" ,then again it says "it doesn't affect the OS on member servers and workstations" ! I am really confused. Please can anyone help me on these points? With best regards

netsysllc · March 2014

If you network had only one Domain Controller running 2003 the highest level would be 2003, but you can have non Domain Controller member servers at any level joined to the network 2008, 2008R2, 2012 or 2012R2.

maybe this will help Understanding Domain and Forest Functional Levels

john_samson · March 2014

Hi Thanks for reply. But then what does this statement mean - The functional level of a domain or forest does not affect the operating system that you can use on member servers and workstations that are joined to a domain or forest? Does it mean that if the Domain Func level is 2008 ,still we can add any members within it running any version of Windows like XP,Vista,2003 or 2000? It is not clear.

netBooger · March 2014

The statement is accurate. The statement "The functional level of a domain or forest does not affect the operating system that you can use on member servers and workstations that are joined to a domain or forest?" is referring to everything excluding Domain Controllers. The key words to point out are member servers and workstations. Member servers do not include Domain Controllers. So yes you can have a Domain at any functional level and run any Member/Workstation OS.

In other words, the only time you are restricted to what OS you can run in a Domain pertains only to Domain Controllers.

With that said however, the forest/domain functional levels can affect the features/applications available across the forest/domain.

Doubts regarding Domain and Forest Functional Levels

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