Updated on September 27, 2023
Active Directory (AD) and a domain controller are some of the IT components that are core to organizations using Windows operating systems (OSs). But what’s the difference between them?
Active Directory is Microsoft’s proprietary directory service. It allows IT teams to manage identity and secure access to various resources on the enterprise network.
A domain controller, on the other hand, is a server that responds to user authentication requests, allowing the host to access various resources on an enterprise network.
In this post, we’ll explore the differences between a domain controller versus Active Directory, and how JumpCloud can help you enhance AD or ditch the domain controller altogether.
Active Directory: Identities and Access
Active Directory is an identity management database that allows IT teams to define what users can do on a network. As a database, Active Directory captures data in the form of objects. An object can be a single resource element, like a user, group, application, or device.
Each object has associated attributes that allow it to be distinguished from other entities. For example, a user object would have a username, password, and email attributes that distinguish it from other objects.
Active Directory consists of four essential services that allow it to provide identity and access management:
Active Directory Domain Services (AD DS)
This is the main service within the Active Directory protocol. Besides storing the directory information, it also controls which users can access each enterprise resource and group policies. AD DS uses a tiered structure comprising the domains, trees, and forests to coordinate networked resources.
Active Directory Lightweight Directory Services (AD LDS)
It shares the same codebase and functionality as AD DS. However, unlike AD DS, AD LDS uses the Lightweight Directory Access Protocol (LDAP), allowing it to run on multiple instances on the same server.
Active Directory Federation Services (AD FS)
As the name suggests, AD FS is a federated identity service that provides single sign-on (SSO) capabilities. It uses many popular protocols such as OAuth, OpenID, and Secure Assertion Markup Language (SAML) to pass credentials between different identity providers.
Active Directory Certificate Services (AD CS)
This is a service that creates on-premises public key infrastructure (PKI), allowing organizations to create, validate, and revoke certificates for internal use.
Domain Controller: Validate and Authenticate
A domain controller is a server that processes user authentication requests on a particular domain on an enterprise network. While domain controllers are primarily used in AD domains, you can also use them with other non-Windows identity and access management (IAM) systems, such as Samba and FreeIPA.
A domain controller restricts access to enterprise resources within a given domain by authenticating and authorizing users based on their login credentials. For example, in Windows domains, the domain controller obtains authentication information for user accounts from Active Directory.
While domain controllers can operate as single systems, they are often implemented in clusters to provide high availability (HA) and reliability services. For example, in Windows Active Directory, each cluster can consist of a primary domain controller (PDC) and a backup domain controller (BDC). In Unix and Linux ecosystems, replica domain controllers replicate authentication databases from the PDC.
Active Directory vs. Domain Controller
It’s common to think that the terms Active Directory and domain controller are synonymous. This is because domain control is a function within Microsoft’s Active Directory, and domain controllers are servers that leverage AD to validate and respond to authentication requests.
However, the terms are not interchangeable. Active Directory is a database that stores and organizes enterprise resources as objects. You can think of Active Directory as a database that stores users and device configurations in AD DS. A domain controller, in contrast, is simply a server running Active Directory that authenticates users and devices. In this regard, you can think of a domain controller as a custodian, facilitator, or host of Active Directory.
Since domain controllers mediate all access to the network resources, it is essential to protect them with additional security mechanisms, such as firewalls, encryption protocols, and expedited configuration and patch management solutions.
Deciding What You Need for a Directory and Domain Controller
Many organizations are looking to implement SSO solutions that allow their employees to access all their on-prem and cloud-based applications easily.
In the recent past, a vital requirement of these solutions was the domain controller, which made it possible to connect applications back to Active Directory as a single source of truth. Organizations have used AD FS as a solution for integrating Active Directory into cloud-based applications. However, while Microsoft markets AD FS as a “free” solution, there are many hidden costs, including hardware purchase, deployment, and ongoing maintenance, that you have to contend with.
But suppose you were to decide what you need for a directory or what constitutes a complete IAM solution today. Such a solution should provide automated provisioning of resources, lifecycle management, mobile device management (MDM), and reporting from a single console. The IAM solution should also be vendor-agnostic, unlike Active Directory, which excels at managing access to on-prem Windows-based OSs. The IT environments of today simply don’t look like that anymore.
The JumpCloud Directory Platform® is a low-cost, cloud-based directory management solution that simplifies AD integration, allowing IT teams to unify IAM and consolidate tooling while enhancing Active Directory’s functionality. Organizations can also leverage JumpCloud as an AD replacement tool, reducing the on-prem servers required to set up AD FS and moving to a domainless enterprise.
Active Directory & Domain Controller FAQs
Are domain controllers and Active Directory the same thing?
No, Active Directory is a directory service that stores information, whereas a Domain Controller is a server that runs Active Directory and is responsible for authenticating users and enforcing security policies within the domain.
Can a network have multiple domain controllers?
Yes, a network can have multiple domain controllers for high availability. Having multiple domain controllers provides fault tolerance and ensures network availability even if one domain controller fails. Changes to Active Directory are replicated between domain controllers to keep the information consistent. Cluster Aware Updating is used to update the cluster nodes.
Can Active Directory be installed on a non-Windows server?
No, Active Directory is a Microsoft technology and can only be installed on Windows Server operating systems.
Does Active Directory support multi-domain environments?
Yes, Active Directory supports multi-domain environments. It can manage multiple domains within a forest, and trust relationships can be established between domains to allow resource access across domains. This requires following security best practices, selecting the appropriate trust relationship(s), avoiding single points of failure, and having the appropriate security controls so that attackers cannot move laterally across domains. You also want to ensure that your environment isn’t too complex to manage.
How does a domain controller handle user authentication?
A domain controller uses the authentication protocol Kerberos to verify the identity of users and computers within the domain. When a user attempts to log in, the domain controller checks the credentials against the Active Directory database before granting access to network resources.
Windows NT LAN Manager (NTLM) authentication is also still supported by Microsoft.
Can a domain controller be a physical or virtual server?
Yes, a domain controller can be either a physical server or a virtual machine run on premises or in the cloud. As long as it meets the hardware requirements and runs a compatible Windows Server operating system, it can function effectively as a domain controller.
What is the process of promoting a server to a domain controller?
Promoting a server to a domain controller involves installing the Active Directory Domain Services role, running the Active Directory Domain Services Configuration Wizard, selecting the appropriate options, and defining the domain configuration. You may add your new domain controller to an existing domain for high availability. This work should be performed from a secure workstation while using temporarily elevated access for global admin rights.
What is the Global Catalog in a domain controller?
The Global Catalog is a distributed data repository in a domain controller that contains a partial replica of all objects from all domains within the Active Directory forest. It allows for efficient searching and authentication across the forest.
How does a domain controller handle group policies?
Group Policies in Active Directory allow administrators to control user and computer configurations across the domain. The domain controller replicates and enforces these policies to all machines within its domain, ensuring consistent settings and security measures.
Can a domain controller operate independently without a network connection?
While a domain controller can function independently for a limited time, it requires network connectivity to provide essential services like user authentication, access to resources, and replication with other domain controllers for full functionality.
How can I monitor the health of domain controllers?
You can monitor domain controllers using tools like Windows Server’s Event Viewer and Performance Monitor. Regularly check for critical events, performance metrics, and ensure replication between domain controllers is functioning correctly. Some organizations also utilize Security information and event management (SIEM) and other security services.
How do domain controllers contribute to network security?
Domain controllers play a crucial role in network security by enforcing user access controls, implementing group policies, facilitating secure communication through encryption, and ensuring the integrity and availability of Active Directory data.
What are some best practices to enhance domain controller security?
First, consider the physical security of your servers and establish procedures to restrict access. Implement role-based separation of duties, such as Shielded VMs in Hyper-V Secure, if you collocate less sensitive virtual machines on the same physical infrastructure.
Secure the control plane by following guidance to reduce the attack surface area through configuration management. Microsoft’s documentation on securing privileged access is helpful for those purposes. Limit internet access by using policies to restrict web browsing from your domain controllers.
Privileged users should ideally be issued just-in-time rights for privileged access to production servers and reside in a secure bastion forest to avoid granting attackers untethered access to domain-joined IT infrastructure. Only run currently supported versions of Windows Server (upgrading domain and forest functional levels) and adopt a patch management strategy to control vulnerabilities.
Also, secure Active Directory Federation Services (AD FS) if it’s part of your environment. Larger organizations will always monitor for signs of compromise and scan for known vulnerabilities.
How does Active Directory ensure data consistency across domain controllers?
Active Directory maintains data consistency through multi-master replication. Each domain controller holds a writable copy of the Active Directory database, and changes made to one domain controller are replicated to others within the domain.
Can a domain controller be assigned multiple roles in Active Directory?
Yes, a domain controller can hold multiple roles known as Flexible Single Master Operations (FSMO) roles. These roles include Schema Master, Domain Naming Master, PDC Emulator, RID Master, and Infrastructure Master. However, domain controllers should have a limited number of roles installed on them. Security risks increase when more software is running. Windows Server Core is an installation option that will reduce the attack surface area.
What is the purpose of the Global Catalog in Active Directory domain controllers?
The Global Catalog stores a partial replica of all objects in the forest, enabling efficient searches across domains and providing universal group membership information during user authentication.
What is the process of removing a retired or decommissioned domain controller from Active Directory?
To remove a retired or decommissioned domain controller, you should demote it using the DCPROMO utility or by using PowerShell and then following the appropriate removal workflow. This ensures that Active Directory is aware of the changes and avoids potential issues with metadata. Follow best practices to ensure that all of the FSMO roles have been transferred to other servers and the global catalog isn’t impacted by the demotion.
Can I rename a domain controller in Active Directory?
Renaming a domain controller within Active Directory is not recommended as it can lead to complications, such as replication issues and service failures. It’s best to avoid renaming domain controllers, unless you first demote them and later promote them back to a member server.
How can I optimize replication between domain controllers in a geographically distributed environment?
In a geographically distributed environment, you can optimize replication by implementing Active Directory Sites and Services, configuring site links with appropriate replication intervals, and placing domain controllers in the correct sites. Follow best practices when designing and planning the site topology to ensure efficient routing of query and replication traffic
How do I recover a failed domain controller in Active Directory?
If a single domain controller fails, attempt to restore it from a system backup (system state) or rebuild it using the same settings such as name and IP address, DNS server settings, subnet, etc. You’ll be using Directory Services Restore Mode (DSRM) safe boot option. A bare metal backup may become necessary if there is no existing operating system present.
Consider a replication recovery strategy if the domain controller is a cluster node. It’s also important to know the difference between an authoritative and non-authoritative recovery, because it will affect other member nodes. If a full restoration is not possible, you may need to seize FSMO roles on another healthy domain controller and perform metadata cleanup.