How to Add a New Domain Controller to an Existing Windows Server 2012 Forest or Domain

This post will discuss how to add a new domain controller to an existing Windows Server 2012 Domain Services infrastructure.  This is a continuation of my previous post on How to Install Active Directory from Windows Server 2012 Server Manager which discussing installing a new Active Directory forest.

Adding a second domain controller to a domain is highly recommended for any infrastructure because it adds much more resiliency, up time, and maintainability to your infrastructure and helps replicate the Active Directory data to another system.

We sill start this guide from the Active Directory Domain Services Configuration Wizard. To get to this point, please follow the Installing Active Directory from Windows Server 2012 Server Manager section of my previous post.

Run Active Directory Domain Services Configuration Wizard

• After the role installation completes, you will notice a notification in the Notifications window.  Click the flag and click the link Promote the server to a domain controller

• Deployment Configuration: Select Add a domain controller to an existing domain. Under the Specify the domain information for this operation type in the FQDN of the domain you would like to add this server to.  In this case we are using testlab.local. Finally, Supply the username and password of a domain admin in the domain.  We are using TESTLAB\Administrator.  Click Next
• NOTE:  In our test lab we have each DC in a separate VLAN to represent a different site.  If you are doing this, you may not pick up the domain name automatically and can be presented with an error that the domain cannot be contacted.  To overcome this, set the primary DNS server of the new system to the IP of the existing DC in the domain.

• Domain Controller Options: Select the options you want this DC to have.  We are selecting DNS and GC and for now are adding it to the Default-First-Site-Name site.  We will discuss sites in a later post.  Also add the recovery password for the DC and click Next.

• DNS Options: Click Next

• Additional Options:  You can choose to install the AD database from media but we will choose to replicate the database from our first DC AZ-DC1.testlab.local.  You can also select Any Domain Controller and AD will use sites and and site links to determine the best domain controller to replicate from.  Click Next

• Paths: Verify the paths for the AD database, Log files and SYSVOL share and click Next
• The AD database and SYSVOL location can be changed but is usually left as default.  Personally, I install all DCs with a single partition and keep the system very trim so I never change the path of the database or SYSVOL share.

• Prerequisites Check: 
• This will validate that the server is ready for Domain Services and will show a couple warnings about NT 4.0 compatibility and the same warning from the DNS delegation screen.  These are expected.  Click Install to begin the installation of the first DC in the forest.
• NT 4.0 Compatibility
• If you checked the  Restart the destination server automatically if required when installing domain services role the server will reboot automatically after the installation is complete.

• After a reboot and you login to the domain, you will now be able to see the new DC in Active Directory Administrative Center.

This concludes How to Add a New Domain Controller to an Existing Windows Server 2012 Forest or Domain.

I hope this was helpful and informative to you and I would appreciate any feedback you may have.