All though Active Directory has been available for over ten years, one question that comes up time and time again at customer sites is “What do the Forest and Domain Functional Levels do and should I set them?”  After validating their Active Directory my answer is usually yes,  but what do these levels enable within Active Directory?

Domain functional levels

There are six domain functional levels:

The functional level for a domain enables features that affect the only that domain.

Windows 2000 mixed (the default in Windows Server 2003) DFL 0
Windows 2000 native DFL 0
Windows Server 2003 interim DFL 1
Windows Server 2003 DFL 2
Windows Server 2008 DFL 3
Windows Server 2008 R2 DFL 4
Windows Server 2012  DFL 5
Windows Server 2012 R2 DFL 6

Forest functional levels

There are five forest functional levels:

The functional level for a forest enables features in all domains within a forest.

Windows 2000 (the default in Windows Server 2003 and Windows Server 2008) FFL 0
Windows Server 2003 interim FFL 1
Windows Server 2003 (the default in Windows Server 2008 R2) FFL 2
Windows Server 2008 FFL 3
Windows Server 2008 R2 FFL 4
Windows Server 2012  FFL 5
Windows Server 2012 R2 FFL 6

Domain Functional Level

Windows 2000 native

All default Active Directory features and the following features:

Universal groups are enabled for both distribution groups and security groups.

Group nesting.

Group conversion is enabled, which makes conversion possible between security groups and distribution groups.

Security Identifier (SID) history

Supported Domain Controllers

Windows 2000 Server
Windows Server 2003
Windows Server 2008
Windows Server 2008 R2

Windows Server 2003

All default Active Directory features,

All features from the Windows 2000 native domain functional level, plus the following features:

The availability of the domain management tool, Netdom.exe, to prepare for domain controller rename.

Update of the logon time stamp. The lastLogonTimestamp attribute is updated with the last logon time of the user or computer. This attribute is replicated within the domain.

The ability to set the userPassword attribute as the effective password on the inetOrgPerson object and user objects.

The ability to redirect Users and Computers containers. By default, two well-known containers are provided for housing computer and user/group accounts: cn=Computers,<domain root> and cn=Users,<domain root>. This feature makes it possible to define a new well-known location for these accounts.

Authorization Manager can store its authorization policies in AD DS.

Constrained delegation is included, which makes it possible for applications to take advantage of the secure delegation of user credentials by means of the Kerberos authentication protocol. You can configure delegation to be allowed only to specific destination services.

Selective authentication is supported, which makes it possible to specify the users and groups from a trusted forest who are allowed to authenticate to resource servers in a trusting forest.

Supported Domain Controllers

Windows Server 2003
Windows Server 2008
Windows Server 2008 R2

Windows Server 2008

All default Active Directory features, all features from the Windows Server 2003 domain functional level, plus the following features:

Distributed File System Replication support for SYSVOL, which provides more robust and detailed replication of SYSVOL contents.

Advanced Encryption Services (AES 128 and 256) support for the Kerberos authentication protocol.

Last Interactive Logon Information, which displays the time of the last successful interactive logon for a user, from what workstation, and the number of failed logon attempts since the last logon.

Fine-grained password policies, which make it possible for password policies and account lockout policies to be specified for users and global security groups in a domain.

Supported Domain Controllers

Windows Server 2008
Windows Server 2008 R2

Windows Server 2008 R2

All default Active Directory features, all features from the Windows Server 2008 domain functional level, plus the following features:

Authentication mechanism assurance, which packages information about the type of logon method (smart card or user name/password) that is used to authenticate domain users inside each user’s Kerberos token. When this feature is enabled in a network environment that has deployed a federated identity management infrastructure, such as Active Directory Federation Services (AD FS), the information in the token can then be extracted whenever a user attempts to access any claims-aware application that has been developed to determine authorization based on a user’s logon method.

Supported Domain Controllers

Windows Server 2008 R2

Windows Server 2012

All default Active Directory features, all features from the Windows Server 2008 R2 domain functional level, plus the following features:

The KDC support for claims, compound authentication, and Kerberos armoring.

Supported Domain Controllers

Windows Server 2012
Windows Server 2012 R2

Windows Server 2012 R2

All default Active Directory features, all features from the Windows Server 2012 domain functional level, plus the following features:

DC-side protections for Protected Users. Protected Users authenticating to a Windows Server 2012 R2 domain can no longer:

  • Authenticate with NTLM authentication
  • Use DES or RC4 cipher suites in Kerberos pre-authentication
  • Be delegated with unconstrained or constrained delegation
  • Renew user tickets (TGTs) beyond the initial 4 hour lifetime

Authentication Policies

New forest-based Active Directory policies which can be applied to accounts in Windows Server 2012 R2 domains to control which hosts an account can sign-on from and apply access control conditions for authentication to services running as an account.

Authentication Policy Silos

New forest-based Active Directory object, which can create a relationship between user, managed service and computer, accounts to be used to classify accounts for authentication policies or for authentication isolation.

 

Supported Domain Controllers

Windows Server 2012 R2

Forest Functional Level

Windows 2000 ServerAll default Active Directory features, plus the following features:

Supported Domain Controllers

Windows NT 4.0
Windows 2000
Windows Server 2003
Windows Server 2008
Windows Server 2008 R2

Windows Server 2003

All default Active Directory features, plus the following features:

Forest trust

Domain rename

Linked-value replication (Changes in group membership store and replicate values for individual members instead of replicating the entire membership as a single unit.) This results in lower network bandwidth and processor usage during replication and eliminates the possibility of lost updates when different members are added or removed concurrently at different domain controllers.

The ability to deploy a read-only domain controller (RODC) that runs Windows Server 2008.

Improved Knowledge Consistency Checker (KCC) algorithms and scalability. The intersite topology generator (ISTG) uses improved algorithms that scale to support forests with a greater number of sites than can be supported at the Windows 2000 forest functional level.

The ability to create instances of the dynamic auxiliary class called dynamicObject in a domain directory partition.

The ability to convert an inetOrgPerson object instance into a User object instance, and the reverse.

The ability to create instances of the new group types, called application basic groups and Lightweight Directory Access Protocol (LDAP) query groups, to support role-based authorization.

Deactivation and redefinition of attributes and classes in the schema.

Supported Domain Controllers

Windows Server 2003
Windows Server 2008
Windows Server 2008 R2

Windows Server 2008

This functional level provides all of the features that are available at the Windows Server 2003 forest functional level, but no additional features.

Supported Domain Controllers

Windows Server 2008
Windows Server 2008 R2

Windows Server 2008 R2

All of the features that are available at the Windows Server 2008 forest functional level, plus the following features:

Active Directory Recycle Bin, which provides the ability to restore deleted objects in their entirety while AD DS is running.

Supported Domain Controllers

Windows Server 2008 R2

Windows Server 2012

All of the features that are available at the Windows Server 2008 R2 forest functional level, but no additional features.

All domains that are subsequently added to the forest will operate at the Windows Server 2012 domain functional level by default.

Supported Domain Controllers

Windows Server 2012
Windows Server 2012 R2

Windows Server 2012 R2

All of the features that are available at the Windows Server 2012 forest functional level, but no additional features.

All domains that are subsequently added to the forest will operate at the Windows Server 2012 R2 domain functional level by default.

Supported Domain Controllers

Windows Server 2012 R2

Posted by markparris

Microsoft MVP - Enterprise mobility.

3 Comments

  1. […] Hi ionee, What are exactly the functional levels of your forest and domain? Thank You. Active Directory Domain and Forest Functional Levels | Mark Parris […]

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  2. […] install in a Forest / Domain that has never had Exchange before, you will need to ensure that the Forest Functional level is at least “Windows Server 2003” – you will need to consider which level you set […]

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