Add 2012 Functional Level child domain to 2003 forest

A regional centre of a large global client wants to leverage some of the new features in 2012 (particularly DC snapshots and Dynamic Access Control). The global corp forest is at 2003 Forest Functional Level (FFL), and there are no plans to raise anytime soon. I suggested we look at adding a 2012 Domain Functional Level child, but Understanding AD Functional Levels does not list this as an option. So I ran a quick test, creating a vanilla 2003 domain then trying to add a vanilla 2012 child. I first got this:

Oops, forgot a new 2003 domain gets created at 2000 Native level. I raised to 2003 domain/forest functional level and tried again:

So turns out it IS an allowed configuration. The only feature enabled by having a higher FFL is AD Recycle Bin (from 2008 R2 FFL), and sure enough when I tried with the Enable-ADOptionalFeature cmdlet it was not possible to enable this.

Initially promising then, but more testing needed to see if it meets the client’s functionality requirements.