When you use Windows Server 2012 Server Manager to install Active Directory Domain Services (AD DS) on an additional domain controller or on the first domain controller in a new child or tree domain, the Next button is never available on the Domain Controller Options page. For example:
This prevents the installation of AD DS on the domain controller.
This issue occurs for one of the following reasons:
You didn't type and confirm a Directory Services Restore Mode (DSRM) password.
Your forest contains more than one site, and the computer on which you are installing AD DS belongs to an IP subnet that is not defined or is not associated with a logical site. Notice that in the screen shot, the Site name list is empty. This means that no site could be automatically selected.
There are two possible resolutions for the second cause. The first resolution is to make sure that all network subnets are defined in the forest and that all sites in the topology have valid associated subnets. You can do this by using Dssite.msc or the Windows Server 2012 version of the Active Directory Windows PowerShell module. After you do this, you should try to install AD DS again by using Server Manager. The correct site will be detected automatically.
We recommend this resolution.
The second resolution is to select the correct site name from the Site name list manually. For example:
We do not recommend this resolution as strongly because it masks the underlying problem. This is that clients, servers, and domain controllers that are not associated with AD DS sites correctly do not work efficiently with DFS Namespace referrals, Windows Server 2012 Direct Access, or other site-aware technologies. One or more incorrectly designed sites and subnets are present in the forest.
To detect all AD DS sites that are missing associated subnets, you can use the following sample Windows Server 2012 Active Directory Windows PowerShell command: