If you want to study Active Directory at home and install it on a machine that has a disconnected network cable; or if you want to install AD on a server whose network cable is disconnected, you can't because your network cable is disconnected. You can't even see IP config from the command prompt and DCpromo.exe do allow you to continue. Here is a solution:
Install Microsoft Lopback Adapter.
- From Hardware Wizard, add new device.
- Select network adapter.
- From the left, choose Microsoft from Manufacturers window.
- Choose Microsoft Lopback adapter from the right.
- Now give an IP to this adapter. (It is always up an running.)
You can now install Active Directory.