Add a new domain to an existing forest

To add a new domain to an existing forest, you'll need to follow these steps:

Prerequisites:

  1. You have an existing forest with at least one domain controller.
  2. You have a new domain name and a DNS server that can resolve the new domain name.
  3. You have a Windows Server operating system with the Active Directory Domain Services (AD DS) role installed.

Step 1: Prepare the new domain

  1. Create a new domain controller for the new domain. You can do this by installing a new Windows Server operating system with the AD DS role, and then promoting it to a domain controller.
  2. Configure the new domain controller with the new domain name and DNS settings.
  3. Make sure the new domain controller is a member of the existing forest by joining it to the forest using the djoin command or by using the Active Directory Domain Services Configuration Wizard.

Step 2: Add the new domain to the forest

  1. Open the Active Directory Domains and Trusts snap-in (dsa.msc) on a domain controller in the existing forest.
  2. Right-click on the forest and select "New Domain in Forest".
  3. Enter the name of the new domain and the DNS server that will be used to resolve the new domain name.
  4. Click "Next" and then "Finish" to create the new domain.

Step 3: Configure the new domain

  1. Promote the new domain controller to a domain controller for the new domain.
  2. Configure the new domain with the necessary settings, such as the domain functional level, forest functional level, and DNS settings.
  3. Make sure the new domain is properly integrated with the existing forest by configuring trust relationships and DNS settings.

Step 4: Verify the new domain

  1. Verify that the new domain is properly added to the forest by checking the Active Directory Domains and Trusts snap-in.
  2. Verify that the new domain is properly configured by checking the DNS settings and the domain functional level.
  3. Verify that users and computers can authenticate to the new domain by testing logon and authentication.

Additional considerations:

  1. Make sure to plan for domain controller placement and replication to ensure that the new domain is properly replicated across the forest.
  2. Consider configuring a trust relationship between the new domain and the existing domain to allow for authentication and resource access between the two domains.
  3. Make sure to update any DNS settings and firewall rules to allow for communication between the new domain and the existing domain.

By following these steps, you should be able to add a new domain to an existing forest.