http://www.cnblogs.com/westsource/archive/2012/12/26/2834876.html
If you have Windows Server 2012 iso file or DVD, you can install .net framework 3.5 on Windows Server 2012 easly.
1. You have to insert Windows Server 2012 DVD or iso to D drive.
2. Open Add Roles and Features Wizard
3. Select .NET Framework 3.5 Features and then click next,
4. Select Specify an alternate source path link in the Confirm installation selections screen.
5. Path: D:\Sources\SxS and then click OK.
6. Finally click Install button.
Hello,
Do you have access to internet with this machine ?
Using dism.exe should solve your problem if you have ISO or the dvd in the machine :
step1
dism.exe /online/enable-feature/featurename:NetFX3/Source:D:\sources\sxs/LimitAccess
D:\ = drive or cd with the cabs maybe you have another leather
step 2
dism.exe /online/enable-feature/featurename:NetFX3 /all
after these steps i join to the domain
i did it in thease way
regards