I am migrating our company's AD from a Windows SBS 2008 to a news Windows 2012 R2 Essentials server. Everything went fine and the new AD now is in production stage. The last step is adding an additional DC to the new domain for replica pourposes: I need to promote a Windows Server 2008 R2 that used to do the same in the old SBS domain.
The problem that arises when trying to use the dcpromo command is the following: "The Functional Level of the forest is incompatible with this operating system"
I understand that I need to lower the Active Directory domain/forest Functional Level from 2012/2012R2 to 2008 R2, but I would like to understand how this could affect the current domain (and the attached clients).
Thanks