First remove windows update KB below if installed.
- KB2966826
- KB2966827
- KB2966828
Method 1
1. Add feature, select .Net Framework 3.5 features
2. Select Specify an alternate sources path (highlighted)
3. Enter D:\Sources\SxS\ (D: = Windows server installation kit or mount the ISO, my drive here is D:)
4. .NET Framework installed.
Note: If unable to install, try copy ISO to local disk and mount agains, or change another installation kit.
