We have a new Forest with a Domain Controler. We want to add a new domain controler. We configure a new Windows 2012 server and add this server into the domain.
Restart the server, and go to Add roles and Features Wizard. Select the rol Active Directory Domain Services.
When the installation finish, we need to promote the Domain Controler Server. In the top of Service Manager, appear a flag with a warning. We select this and press in "Promote this server to a domain controller"
Select Add a domain Controler to an existing domain, and write the domain. In our case domain.com.
In this screen we can select if our new server will be DNS and Global Catalog (A global catalog server is a domain controller that stores a full copy of all objects in the directory for its host domain and a partial, read-only copy of all objects for all other domains in the forest.) or Read only domain Controler (RODCs are additional domain controllers for a domain that host complete, read-only copies of the partitions of the Active Directory database and a read-only copy of the SYSVOL folder contents.). I select DNS and GC, but you can configure the server as RODC.
In Additional Option we can select the Replicate Server. We can chose any domain controler in the domain or one server
When the installation finish. We can see the new Domain Controler is in the new Domain and appear in Sites and Services