Understanding Windows Server 2008 Active Directory Domain and Forest Functional Levels

In Windows Server 2003, functional levels were an extension of the older mixed/native mode concept introduced in Windows 2000. In Windows Server 2008 this was further extended to include new features and benefits, and are used to activate new Active Directory features after all the Domain Controllers (DCs) in the domain or forest are running Windows Server 2008 operating systems. Functional levels determine the features of Active Directory Domain Services (AD DS) that are enabled in a domain or forest.

When the first Windows Server 2008–based Domain Controller is deployed in a domain or forest, the domain or forest operates by default at the lowest functional level that is possible in that environment, meaning Windows 2000 Native Mode. This allows you to take advantage of the default Active Directory features while running versions of Windows earlier than Windows Server 2008. When you raise the functional level of a domain or forest, a set of advanced features becomes available.

After the domain functional level is raised, DCs that are running earlier operating systems cannot be introduced into the domain. For example, if you raise the domain functional level to Windows Server 2008, Domain Controllers that are running Windows Server 2003 cannot be added to that domain.

Unless you still have old NT 4.0 BDCs there's no reason for staying in Mixed Mode, and as you already know, Windows Server 2008 does not support NT 4.0 BDCs, so if you are still using them and planning to upgrade your Active Directory to Windows Server 2008, re-think your strategy.

As for Windows 2000 Native Mode, unless you still have Windows 2000 Domain Controllers, again, there's no reason for staying in that function level. However, if you still do, remember that Windows Server 2008 does only supports Windows 2000 SP4. Be sure to have SP4 on all your Windows 2000 DCs.

You can read my "What are the domain and forest function levels in a Windows Server 2003-based Active Directory?" article for more info about that.

Note: Network clients can authenticate or access resources in the domain or forest without being affected by the Windows Server 2003 or Windows Server 2008 domain or forest functional levels. These levels only affect the way that domain controllers interact with each other. However, be aware of the fact that regardless of the domain or function level, servers running Windows NT Server 4.0 are NOT supported by domain controllers that are running Windows Server 2008, meaning you MUST have additional DCs running Windows 2000/2003 to support older NT 4.0 servers.

For more information about Windows Server 2008 Active Directory requirements, please read my "Active Directory on Windows Server 2008 Requirements" article.

Read my "Raising Windows Server 2008 Active Directory Domain and Forest Functional Levels" article for information on how to actually raise the domain and forest function levels.

Domain Function Levels

To activate a new domain function level, all DCs in the domain must be running the right operating system. After this requirement is met, the administrator can raise the domain functional level. Here's a list of the available domain function levels available in Windows Server 2008:

Windows 2000 Native Mode

This is the default function level for new Windows Server 2008 Active Directory domains.

Supported Domain controllers – Windows 2000, Windows Server 2003, Windows Server 2008.

Features and benefits:

• Group nesting – Unlike Windows NT 4.0, allows placing of a group of one scope as a member of another group of the same scope.
• Universal security groups – Allows usage of Universal security type groups.
• SidHistory – Enables usage of SidHistory when migrating objects between domains.
• Converting groups between security groups and distribution groups – Unlike Windows NT 4.0, allows converting of a group type into another group type (with some limitations).

Windows Server 2003 Mode

To activate the new domain features, all domain controllers in the domain must be running Windows Server 2003. After this requirement is met, the administrator can raise the domain functional level to Windows Server 2003. Read my "Raise Domain Function Level in Windows Server 2003 Domains" article for more info about that.

Supported Domain controllers – Windows Server 2003, Windows Server 2008.

Features and benefits include all default Active Directory features, all features from the Windows 2000 native domain functional level, plus:

• Universal group caching – Windows Server 2003 functional level supports Universal group caching which eliminate the need for local global catalog server.
• Domain Controller rename – By using the NETDOM command.
• Logon time stamp update – The lastLogonTimestamp attribute will be updated with the last logon time of the user or computer. This attribute is replicated within the domain.
• Multivalued attribute replication improvements – Allows incremental membership changes, which in turn enables having more than 5000 members in a group and better replication capabilities.
• Lingering objects (zombies) detection – Windows Server 2003 has the ability to detect zombies, or lingering objects.
• AD-integrated DNS zones in application partitions – This allows storing of DNS data in AD application partition for more efficient replication.
• Users and Computers containers can be redirected – This allows the redirection of the default location of new users and computers (by using the REDIRUSR and REDIRCMP commands).
• Support for selective authentication – 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.

Windows Server 2008 Mode

To activate the new domain features, all domain controllers in the domain must be running Windows Server 2008. After this requirement is met, the administrator can raise the domain functional level to Windows Server 2008.

Important

Raising the domain and forest functional levels to Windows Server 2008 is a nonreversible task and prohibits the addition of Windows 2000–based or Windows Server 2003–based Domain Controllers to the environment. Any existing Windows 2000–based or Windows Server 2003–based Domain Controllers in the environment will no longer function, and in fact, the upgrading wizard will not allow you to continue with the operation. Before raising functional levels to take advantage of advanced Windows Server 2008 features, ensure that you will never need to install domain controllers running Windows 2000-based or Windows Server 2003–based Domain Controllers in your environment.

Supported Domain controllers – Windows Server 2008.

Features and benefits include all default Active Directory features, all features from the Windows Server 2003 domain functional level, plus:

• Fine-grained password policies – Allows multiple password polices to be applied to different users in the same domain.
• Read-Only Domain Controllers – Allows implementation of domain controllers that only host read-only copy of NTDS database.
• Advanced Encryption Services – (AES 128 and 256) support for the Kerberos protocol.
• Granular auditing – Allows history of object changes in Active Directory.
• Distributed File System Replication (DFSR) – Allows SYSVOL to replicate using DFSR instead of older File Replication Service (FRS). It provides more robust and detailed replication of SYSVOL contents.
• Last Interactive Logon Information – 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.

Forest function levels

Forest functionality activates features across all the domains in your forest. To activate a new forest function level, all the domain in the forest must be running the right operating system and be set to the right domain function level. After this requirement is met, the administrator can raise the forest functional level. Here's a list of the available forest function levels available in Windows Server 2008:

Windows 2000 forest function level

This is the default setting for new Windows Server 2008 Active Directory forests.

Supported Domain controllers in all domains in the forest – Windows 2000, Windows Server 2003, Windows Server 2008.

Windows Server 2003 forest function level

To activate new forest-wide features, all domain controllers in the forest must be running Windows Server 2003. Read my "Raise Forest Function Level in Windows Server 2003 Active Directory" article for more info about that.

Supported Domain controllers in all domains in the forest – Windows Server 2003, Windows Server 2008.

Features and benefits include all default Active Directory features, plus the following features:

• Forest trust.
• Domain rename.
• Linked-value replication – Changes in group membership to store and replicate values for individual members instead of replicating the entire membership as a single unit.
• Deployment of an RODC.
• Intersite topology generator (ISTG) improvements – Supports a more efficient ISTG algorithm allows support for extremely large numbers of sites.
• The ability to create instances of the dynamicObject dynamic auxiliary class.
• 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.

Windows Server 2008 forest function level

To activate new forest-wide features, all domain controllers in the forest must be running Windows Server 2008. Read my "Raising Windows Server 2008 Active Directory Domain and Forest Functional Levels" article for more info about that.

Supported Domain controllers in all domains in the forest – Windows Server 2008.

Features and benefits include all of the features that are available at the Windows Server 2003 forest functional level, but no additional features. All domains that are subsequently added to the forest will operate at the Windows Server 2008 domain functional level by default.

Related Articles

• Raising Windows Server 2008 Active Directory Domain and Forest Functional Levels
• Understanding Function Levels in Windows Server 2003 Active Directory
• Raise Forest  Fuction Level in Windows Server 2003 Active Directory
• Installing Active Directory on Windows Server 2008

Installing Active Directory on Windows Server 2008

In Windows Server 2003, functional levels were an extension of the older mixed/native mode concept introduced in Windows 2000. In Windows Server 2008 this was further extended to include new features and benefits, and are used to activate new Active Directory features after all the Domain Controllers (DCs) in the domain or forest are running Windows Server 2008 operating systems. Functional levels determine the features of Active Directory Domain Services (AD DS) that are enabled in a domain or forest.

Considerations when Installing a new Windows Server 2008 forest

When you install AD to create the first domain controller in a new Windows Server 2008 forest, you must keep the following considerations in mind:

• You must make forest and domain functional level decisions that determine whether your forest and domain can contain domain controllers that run Windows 2000 Server, Windows Server 2003, or both. To read more about forest and domain functional levels please refer to the links below.
• Domain controllers running the Microsoft Windows NT Server 4.0 operating system are NOT supported with Windows Server 2008.
• Servers running Windows NT Server 4.0 are NOT supported by domain controllers that are running Windows Server 2008, meaning you MUST have additional DCs running Windows 2000/2003 to support older NT 4.0 servers.
• The first Windows Server 2008 domain controller in a forest must be a global catalog server and it cannot be an RODC.

Considerations when Installing a new Windows Server 2008 domain in an existing Windows 2000/2003 forest

When you install AD to create the first domain controller in a new Windows Server 2008 domain, you must keep the following considerations in mind:

• Before you create a new Windows Server 2008 domain in a Windows 2000/2003 forest, you must prepare the forest for Windows Server 2008 by extending the schema (that is, by running ADPREP /forestprep). To read more about ADPREP please refer to the links below or my "Windows Server 2008 ADPREP" article.
• You must make domain functional level decisions that determine whether your domain can contain domain controllers that run Windows 2000 Server, Windows Server 2003, or both. To read more about forest and domain functional levels please refer to the links below.
• I recommend that you host the PDC emulator operations master role in the forest root domain on a domain controller that runs Windows Server 2008. For more information about FSMO Roles, please read my "Understanding FSMO Roles in Active Directory" and "Transferring FSMO Roles" articles.

General considerations

Make sure you read and follow the requirements described in my "Active Directory on Windows Server 2008 Requirements" article.

Installing Active Directory Domain Services (AD-DS)

In Windows Server 2008, unlike previous server operating Systems, there is an additional step that needs to be taken before running DCPROMO to promote the server to Domain Controller and installing Active Directory on it. This step is the installation of Active Directory Domain Services (AD-DS) role on the server. In fact, the AD-DS role is what enables the server to act as a Domain Controller, but you will still need to run DCPROMO the regular way.

AD-DS can be installed in one of 3 methods:

Method 1 – Server Manager/Initial Configuration Tasks

Roles can and should be added from Server Manager (but they can also be initiated from the Initial Configuration Tasks wizard that auto-opens the first time you log on to the server).

1. Open Server Manager by clicking the icon in the Quick Launch toolbar, or from the Administrative Tools folder.
2. Wait till it finishes loading, then click on Roles > Add Roles link.

3. In the Before you begin window, click Next.

4. In the Select Server Roles window, click to select Active Directory Domain Services, and then click Next.

5. In the Active Directory Domain Services window read the provided information if you want to, and then click Next.

6. In the Confirm Installation Selections, read the provided information if you want to, and then click Next.

7. Wait till the process completes.

8. When it ends, click Close.

9. Going back to Server Manager, click on the Active Directory Domain Services link, and note that there's no information linked to it, because the DCPROMO command has not been run yet.

10. Now you can click on the DCPROMO link, or read on.


Method 2 – Servermanagercmd.exe

Servermanagercmd.exe is the command prompt equivalent of the Add Roles and Add Features wizards in Server Manager. Through the use of various command line options, you can quickly and easily add or remove features and roles to or from your server, including the AD-DS role.
To install AD-DS by using Servermanagercmd.exe, simply enter the following command in the Command Prompt window:

Servermanagercmd.exe –I ADDS-Domain-Controller

Let the command run and when it finishes, AD-DS will be installed on the server.

Method 3 – Letting DCPROMO do the job

Oh yes. If you forget to install AD-DS or simply want to skip clicking on some windows, you can run DCPROMO from the Run command and before it is executed, the server will check to see if the AD-DS binaries are installed. Since they are not, they will auto-install.

After you complete the Add Roles Wizard, either click the link to start the Active Directory Domain Services Installation Wizard, or close Server Manager and manually run DCPROMO from the Run command.

Running DCPROMO

After installing the AD-DS role, we need to run DCPROMO to perform the actual Active Directory database and function installation.
Note: This guide assumes this is the first Domain controller in the forest, thus creating a new domain in a new forest. For a guide on how to add additional Domain Controllers to existing domains, please read my upcoming "Installing Additional Windows Server 2008 Domain Controllers in your Existing Active Directory Domain" article.
1. To run DCPROMO, enter the command in the Run command, or click on the DCPROMO link from Server Manager > Roles > Active Directory Domain Services.

2. Depending upon the question if AD-DS was previously installed or not, the Active Directory Domain Services Installation Wizard will appear immediately or after a short while. Click Next.

Note: The Advanced features of DCPROMO will be discussed in a future article.
In the Operating System Compatibility window, read the provided information and clickNext.

3. In the Choosing Deployment Configuration window, click on "Create a new domain in a new forest" and click Next.

4. Enter an appropriate name for the new domain. Make sure you pick the right domain name, as renaming domains is a task you will not wish to perform on a daily basis. ClickNext.

Note: Do NOT use single label domain names such as "mydomain" or similar. You MUST pick a full domain name such as "mydomain.local" or "mydomain.com" and so on.
The wizard will perform checks to see if the domain name is not already in use on the local network.

5. Pick the right forest function level. Windows 2000 mode is the default, and it allows the addition of Windows 2000, Windows Server 2003 and Windows Server 2008 Domain Controllers to the forest you're creating. Read my "Understanding Windows Server 2008 Active Directory Domain and Forest Functional Levels" article for more information on that.

6. Pick the right domain function level. Windows 2000 Native mode is the default, and it allows the addition of Windows 2000, Windows Server 2003 and Windows Server 2008 Domain Controllers to the domain you're creating.

Note: If you select "Windows Server 2008" for the forest function level, you will Not be prompted to pick a domain function level. Read more about domain and forest function levels on my "Understanding Windows Server 2008 Active Directory Domain and Forest Functional Levels" article.
7. The wizard will perform checks to see if DNS is properly configured on the local network. In this case, no DNS server has been configured, therefore, the wizard will offer to automatically install DNS on this server.

Note: The first DCs must also be a Global Catalog. Also, the first DCs in a forest cannot be a Read Only Domain controller.
8. It's most likely that you'll get a warning telling you that the server has one or more dynamic IP Addresses. Running IPCONFIG /all will show that this is not the case, because as you can clearly see, I have given the server a static IP Address. So, where did this come from? The answer is IPv6. I did not manually configure the IPv6 Address, hence the warning. In a network where IPv6 is not used, you can safely ignore this warning.

9. You'll probably get a warning about DNS delegation. Since no DNS has been configured yet, you can ignore the message and click Yes.

10. Next, change the paths for the AD database, log files and SYSVOL folder. For large deployments, carefully plan your DC configuration to get the maximum performance. When satisfied, click Next.

11. Enter the password for the Active Directory Recovery Mode. This password must be kept confidential, and because it stays constant while regular domain user passwords expire (based upon the password policy configured for the domain, the default is 42 days), it does not. This password should be complex and at least 7 characters long. I strongly suggest that you do NOT use the regular administrator's password, and that you write it down and securely store it. Click Next.

12. In the Summary window review your selections, and if required, save them to an unattend answer file. When satisfied, click Next.

13. The wizard will begin creating the Active Directory domain, and when finished, you will need to press Finish and reboot your computer.

Note: You can automate the rebooting process by checking the Reboot on Completion checkbox.
To automate domain controller installations, you can use an answer file or you can specify unattended installation parameters at the command line. More on that in my "Creating an Unattend Installation File for DCPROMO in Windows Server 2008" article.
Note: As written in my "Installing Active Directory on Windows 2008 Server Core" article, configuring a Windows Server 2008 Server Core machine REQUIRES you to perform an automated installation of Active Directory on that server, as there is NOT DCPROMO GUI on Server Core.
Your server now acts as a Domain Controller. Make sure you properly back it up. You can test functionality by using AD management tools such as Active Directory Users and Computers, examine the Event Logs, services and folders and shares that have been created.

Links

AD DS Installation and Removal Step-by-Step Guide

Related Articles

• Installing Active Directory on Windows 2008 Server Core
• Raising Windows Server 2008 Active Directory Domain and Forest Functional Levels
• Active Directory on Windows Server 2008 Requirements
• Understanding Windows Server 2008 Active Directory Domain and Forest Functional Levels