Active Directory Domain Services Global Catalogue

Active Directory Domain Services (AD DS) Global Catalog (GC) is a distributed data repository that contains a subset of attributes for all objects in an Active Directory forest. It is designed to improve the performance of searches for objects and their attributes in large and complex network environments.

The Global Catalog is created automatically when the first domain controller in a forest is created. Each domain controller in the forest contains a partial replica of the Global Catalog, which is updated automatically as changes occur in the forest.

The Global Catalog is responsible for several important functions in an Active Directory environment, including:

1. Authentication: The Global Catalog is used to authenticate users who are logging on to the network. When a user logs on, the domain controller that is contacted first checks to see if the user’s credentials are stored in the Global Catalog.
2. Search functionality: The Global Catalog is used to perform global searches for objects and their attributes in the forest. This is particularly useful in large and complex network environments where searching for objects in individual domains can be time-consuming and inefficient.
3. Group membership lookup: The Global Catalog is used to look up group membership information for users in the forest. This allows users to be granted access to resources across multiple domains in the forest.
4. Exchange address book: The Global Catalog is used by Microsoft Exchange to provide the address book functionality for email clients. This allows users to search for email addresses across the entire forest, even if the recipient is located in a different domain.

The Active Directory Domain Services Global Catalog is a distributed data repository that contains a subset of attributes for all objects in an Active Directory forest. It provides several important functions, including authentication, search functionality, group membership lookup, and Exchange address book functionality. By storing a subset of attributes for all objects in the forest, the Global Catalog improves the performance of searches for objects and their attributes in large and complex network environments.

Step-by-Step Guide to making a domain controller a Global Catalog server using both the GUI and PowerShell.

GUI Method:

1. Open the Active Directory Sites and Services console on the domain controller that you want to make a Global Catalog server.
2. Expand the Sites container, and then expand the site that the domain controller belongs to.
3. Expand the Servers container, and then expand the server that you want to make a Global Catalog server.
4. Right-click on NTDS Settings and select Properties.
5. In the Properties window, check the box next to Global Catalog.
6. Click OK to save the changes.
7. Restart the Active Directory Domain Services service on the domain controller.

PowerShell Method:

1. Open PowerShell with administrative privileges.
2. Type the following command to make the domain controller a Global Catalog server:

Set-ADServerSettings -GlobalCatalogEnabled $true

3. Press Enter.
4. Restart the Active Directory Domain Services service on the domain controller.

Note: You can also use the following command to verify whether a domain controller is a Global Catalog server or not:

Get-ADDomainController -Filter * | Format-Table Name,IsGlobalCatalog

This command will list all domain controllers in the domain along with a column indicating whether or not they are Global Catalog servers.