What is Active Directory Global Catalog? How to Define?

  • What is Active Directory Global Catalog? How to Define?

Hello dear readers, in this article we will be talking about the Global Catalog service on Active Directory. After defining it, how do we define it to our Active Directory server? We will be talking. Active Directory (AD) has a feature called the global catalog that enables a domain controller (DC) to offer details on any item in the forest, regardless of whether that object belongs to its domain. Global catalog servers are domain controllers that have the global catalog capability turned on.

First of all, Global Catalog is a service available on DCs, that is, on Domain Controllers. In the initial domain installation configuration, you also install the Global Catalog. We can say that it performs a cache operation for the Global Catalog. It performs a kind of caching operation. I think you will understand it better with an example. I will give an example below.

If there is more than one Tree configuration on the Active Directory server you configured, Global Catalog keeps a copy of the objects on the Tree as "Read-only". In this case, when querying an object or user, it brings you results much faster.

The Global Catalog service must be active so that each forest is hosted on a server in a domain configuration. Of course, since there will be constant replication between Forest and Tree, your bandwidth must be high at the network layer. This configuration can be done not only between Forest and Tree, but also with more than one server with a single domain configuration. Best practices are also recommended for configuration.

What is Active Directory Global Catalog? Core Functionality

In a multi-domain forest setting, global catalog servers are especially crucial for the following tasks:

Authentication. A DC will process the authentication request and deliver permission details for each group the user account belongs to during an interactive domain login. These details will be included in the user access token that is created. The following must be accessed by the DC via a global catalog server.

Resolution of user principal name:

The differentiated name of the related user object must be found in the global catalog for logon requests made with a user principal name (such as "[email protected]").

Group membership at large:

In order to check for any universal groups and identify whether the user signing on is a member of any of them, logon requests issued in multi-domain systems need to use a global catalog. Access to a global catalog server is necessary for authentication in a multi-domain forest since it is the only source of information about universal group membership.

Object Lookup:

Users that do a search can see the directory structure inside a forest thanks to the global catalog. For instance, a user object may be recognized by any global catalog server in a forest using simply its samAccountName. Without a global catalog server, it could be necessary to conduct different searches in each domain in the forest in order to identify a user object using only its samAccountName.

What is Active Directory Global Catalog? How a Global Catalog Works

Active Directory Partitions

It's crucial to first comprehend a little bit about how the Active Directory database is built in order to comprehend how the global catalog functions. The Active Directory database is kept on domain controllers in a single file called NTDS.dit. The database is conceptually divided into partitions to ease management and enable effective replication.

At least three partitions are maintained by each domain controller:

  1. The domain partition has details about the objects and properties of a domain. Every DC has an exact clone of its local domain partition that is readable.
  2. The topology of the forest, including domain controllers and site linkages, is described in the configuration partition.
  3. A fully readable duplicate of the configuration partition is kept on each DC in a forest.
  4. A logical extension of the configuration partition, the schema partition includes definitions for each kind of item in the forest as well as the guidelines for their generation and modification.
  5. The schema partition is maintained in its whole by each DC in a forest. Except for the DC that has the Schema Master operations role for the forest, all DCs have read-only access to the schema partition.

Application partitions may be maintained by domain controllers as well. These partitions may hold any sort of object, with the exception of security principals, and they are used to store information about AD-integrated apps. Application partitions can be configured to replicate to any domain controller (DC) in a forest; they are not needed to replicate to other DCs. Application partitions do not have any special replication requirements.

What is Active Directory Global Catalog? How a Global Catalog Works

Visit! What is Active Directory?

You can identify the partitions present on a DC using the following PowerShell cmdlet:


Get-ADDomainController -Server  | Select-Object -ExpandProperty Partitions 


Global Catalog Partitions

Think about the following forest, which has three domains with one global catalog server each:

Global Catalog Partitions

Every DC keeps a copy of its local domain partition, the configuration partition, and the schema partition, as was previously stated. A second set of read-only partitions are also hosted by global catalog servers in a multi-domain forest like this one. These read-only partitions each include a partial read-only copy of the domain partition from a different domain in the forest. Global catalog servers can execute authentication and forest-wide search queries in a multi-domain forest thanks to the data in these partial, read-only partitions.

The Partial Attribute Set (PAS) refers to the subset of object attributes that are replicated to global catalog servers. This PowerShell cmdlet may list the Partial Attribute Set members in a domain:


Get-ADObject -SearchBase (Get-ADRootDSE).SchemaNamingContext -LDAPFilter "(isMemberOfPartialAttributeSet=TRUE)" -Properties lDAPDisplayName | Select lDAPDisplayName 


Now friends again such an operation In a single domain forest, all DCs host the single domain partition in the forest; therefore, each contains a record of all objects in the forest and can handle authentication and domain service requests. It will be useful for you to know this.

Partial Attribute Set (PAS)

Friends, I am telling you this situation here because I want you to understand the steps better. Now Active Directory takes advantage of this by allowing any domain controller in a single domain forest to operate as a virtual global catalog server, regardless of whether it is configured as a global catalog server, or can also receive that virtual server from the digital ocgean.

Now also: The only limitation is that only DCs configured as global catalog servers can respond to queries specifically for the global catalog. It also responds quickly. We, as the Techdataz team, tested this, dear friends.

Deploying Global Catalog Servers

The first DC will be designated as a global catalog server when a new domain is setup. The Global Catalog checkbox may be enabled in the server's NTDS Settings settings in the Active Directory Sites and Services management console, or the following PowerShell function can be used:


Set-ADObject -Identity (Get-ADDomainController -Server ).NTDSSettingsObjectDN -Replace @{options='1'}  


Visit! Active Directory Group Management Best Practices

To avoid the requirement for an authenticating DC to interact across the network to get global catalog information, each site in the forest should have at least one global catalog server. Universal Group Membership Caching can lower authentication-related network traffic and enable the remote site's DC to process local site login requests using cached universal group membership data in situations where it is not beneficial to deploy a global catalog server in a site ( like a small remote branch office ). This functionality necessitates communication between the remote DC and a global catalog server in order to process initial logons and execute search queries.

Unless there is a compelling explanation not to, it is recommended that all DCs be set up as global catalog servers.



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