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What are FSMO Roles? - The Complete Guide for 2024

What are FSMO Roles? - The Complete Guide for 2024

Let’s first understand:

What is Active Directory?

Microsoft’s proprietary directory service is Active Directory (AD). It runs on Windows Server and allows administrators to manage network rights and access.

Data in Active Directory is stored as objects. A single element, such as a person, group, application, or device like a printer, is referred to as an object. Usually, objects are described as either resource, such as printers or computers, or security principles, such as people or groups.

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What are FSMO Roles?

FSMO (Flexible single master operation) is a Microsoft Active Directory capability that serves as a customized domain controller job when regular data transport and update methods are insufficient.

Tasks that do not adapt themselves to multi-master replication can only be performed as flexible single-master processes.

A single master controls several operators in multi-master setups. This issue is overcome by performing several actions on a single domain controller.

 A single domain controller takes on the function of a particular operation and serves as the sole master for that activity. These activities are known as flexible single-master operations.

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How do FSMO Roles work in Active Directory?

AD was formally unveiled in February 2000 with the Windows 2000 server edition. All of the data and information pertaining to an object and its networks are stored by this access control service.

AD objects include individuals, groups, computers, and printers. Each of these objects has a unique set of properties ascribed to it.

Active Directory has a hierarchical structure that includes domains, trees, and a forest.

  • Domain: It includes elements such as individuals, groups, file servers, computers, and printers.
  • Tree: It is a set of domains. ‘Trusts’ allow objects from various domains to interrelate with one another.
  • Forest: It is the top-level category and consists of a collection of trees. Objects from various forests are unable to communicate with one another, limiting data and information sharing between forests.

Active Directory managers have the power to provide multiple objects privileges and network access.

One of an administrator’s responsibilities is to safeguard the network against malicious attacks and to keep the business secure from any breach. Active Directory’s security measures have altered.

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The Purpose of FSMO Roles


Although multiple upgrades and advancements, Active Directory has issues. The fundamental issue is that when there were several somatic and cognitive, there was redundancy in dealing with changes as DCs argued over who got to implement adjustments. This implied that requests for modifications were probably to be ignored.

Microsoft’s solution:

Microsoft came up with the “Single Master Model” to remedy this, where one domain controller handled verification and the other domain controllers handled updates.

Despite being a big improvement, there were still issues. While the master domain controller remains unavailable, no adjustments could be performed.

Microsoft developed Flexible Single Master Operation (FSMO) Roles for domain controllers in 2003 to address these difficulties. The domain controllers are each given different roles.

One domain controller has no assigned roles. Another domain controller replaces the failed one in the event of a failure.

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What are the FSMO Roles in Active Directory?

The following is a list of the five FSMO roles in active directory:

Types of FSMO Roles
  1. Schema Master FSMO Role
  2. Domain Naming Master FSMO Role
  3. Relative ID (RID) Master FSMO Role
  4. Primary Domain Controller (PDC) Emulator FSMO Role
  5. Infrastructure Master FSMO Role

The first two roles are Schema Master and Domain Naming Master at the forest level while the last three functions(RID Master, PDC Emulator, and Infrastructure Master) are at the Domain level.

Schema Master FSMO Role

The Active Directory schema upgrade is the responsibility of the Schema Master FSMO role. A set of qualities for usage with folder objects makes up the Active Directory schema.

The schema includes characteristics (such as group owner, phone number, and member ID) as well as classes (like category, individual, or msPKI-Key-RecoveryAgent).

Modifications towards the directory schema can only be handled by a DC with Schema Master fsmo role. All the other Domain Controllers in the domain receive the modified schema via replication from the Schema Master. In a forest, there is only one Schema Master.

The Schema Master fsmo role may be used to increase the Active Directory schema to install Exchange or upgrade a forest’s functional level.

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Domain Naming Master FSMO Role

Addition and deletion of domains from Active Directory are handled by the Domain Naming Master fsmo role. You aren’t allowed to create identical domains in a forest with this role.

This assures that every domain web address is distinct. In the existence of this fsmo role, domains cannot be deployed to or withdrawn within Active Directory.

Additionally, this fsmo role has the ability to add and delete domain cross connections from outside directories.

Relative ID Master FSMO Role

A collection of relative identifiers (RIDs) is distributed to every DC by a Relative ID Master Fsmo role. When a Domain Controller creates an object, such a person or an organization, it gives it a special ID called a SID (Security Identification). A SID should be formatted as follows:


Similar to a person’s national id number is a SID. It is distinctive and impossible to duplicate. An item’s SID is associated with the permits and privileges that have been granted to it.

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PDC Emulator FSMO Role

The PDC Emulator FSMO Role can perform the following functions:

PDC Emulator FSMO Role Functions

Time synchronization:

It consolidates the time in a company. All of the Domain Controllers in the domain have their clocks synchronized by the domain controller that plays the PDC Emulator fsmo role. In an Multi Active Directory forest, Domain Controllers holding the Primary Domain Controller Emulator fsmo role coordinate its clock with the Primary Domain Controller Emulator in the parental domain.

Password Changes Performed Using DCs:

Password updates made by other domain controllers are copied to the Primary Domain Controller Emulator. When a DC fails to authenticate because of an invalid password, the failure is sent to the Primary Domain Controller Emulator fsmo role, which compares the request against the most recent passcode to verify it.

Account Lockout is replicated to other DCs:

The Primary Domain Controller Emulator is also useful when accounts are locked. Account lockouts are instantly copied to the other Domain Controllers using the duplicate single object approach. As a result, locked-out accounts cannot access another Domain Controller.

Controls Group Policy:

The Group Policy Management Console (GPMC) utility is in charge of managing group policy. Group Policy Management Console links to the Domain Controller by levant using the Primary Domain Controller Emulator fsmo role to perform modifications in Active Directory. You’ll be prompted to choose an alternate Domain Controller via GPMC if the Primary Domain Controller Emulator isn’t accessible.

Infrastructure Master FSMO Role

An object’s connection to some other domain is determined by its:

  • DN (Distinguished Name)
  • GUID (Globally Unique Identifier)
  • SID (Security Identification)

Updating the SID and differentiating the name of an item in a cross-domain object instance are tasks that belong to the Infrastructure Master. Additionally, this job transfers DNS, SIDs, and GUIDs between forest domains.


FSMO ensures that your domain will be able to carry out its core duty of authenticating users and permissions without interruption (with standard caveats, like the network staying up).

Active Directory FSMO responsibilities are crucial for ensuring AD continues to work as intended. Although you don’t need to worry about FSMO roles most of the time, it’s still crucial to grasp how they work when the time comes!

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About the Author

Technical Lead - AWS Solutions Architect

Shivanshu is a Technical Lead and AWS Solutions Architect passionate about utilizing Cloud technology to empower businesses. Proficient in AWS, Terraform, and GCP, he crafts innovative solutions to propel companies forward. As an enthusiastic writer, he shares his expertise to inspire others in this field.