Raising the domain functional level in Active Directory is like upgrading your phone’s software to unlock new features. It’s something you should do if you’re aiming to take advantage of the latest features, improve security, or ensure that your domain is running smoothly and efficiently. However, this process isn’t something you can just do on a whim—it requires careful planning and the right environment to make sure everything goes off without a hitch. In this article, I’m going to walk you through how to raise the domain functional level and why it matters in simple terms, sharing insights from personal experience and tips I’ve gathered along the way.
Before diving into the process, let’s break down some key points to help you understand:
- Raising the domain functional level unlocks advanced features.
- All domain controllers must run a compatible version of Windows Server.
- The process is irreversible—so make sure you’re prepared.
Understanding Domain Functional Levels
The domain functional level (DFL) determines the set of features that can be used within a domain. Think of it like setting the rules of a game. The higher the level, the more advanced capabilities you get, such as enhanced security features and newer authentication methods.
For example, when you raise the domain functional level to Windows Server 2016, you unlock advanced features like Privileged Access Management (PAM) and improved Kerberos authentication. But it’s not just about the features—it’s about ensuring your domain runs as efficiently and securely as possible. The level also determines which Windows Server versions can act as domain controllers within that domain.
When Should You Raise the Domain Functional Level?
Raising the domain functional level is essential when you want to:
- Leverage new features and enhancements.
- Upgrade security protocols.
- Ensure compatibility with newer versions of Windows Server.
But this decision shouldn’t be rushed. If you’re thinking about raising the functional level, it’s because you’re ready to upgrade and optimize your Active Directory setup. If you’re still running an older version of Windows Server, it’s a good idea to upgrade your domain controllers before making any changes. This way, you avoid compatibility issues and ensure everything runs smoothly.
How to Raise Domain Functional Level: A Step-by-Step Guide
Let’s dive right into the steps for raising your domain functional level. Don’t worry; I’ve broken this down into digestible chunks, so you’ll know exactly what to do.
Step 1: Verify Domain Controller Compatibility
Before you even think about raising the domain functional level, you need to check that all the domain controllers are compatible with the new functional level. This means all your domain controllers should be running a version of Windows Server that supports the new level. For example, to raise to Windows Server 2025, all your domain controllers need to be running Windows Server 2025 or higher.
In my experience, this is often where most admins run into trouble. They forget to upgrade all their domain controllers first, and when they try to raise the level, they get error messages or warnings. Trust me, the last thing you want is to start the process only to realize that not all of your DCs are up to date.
Step 2: Backup Your Active Directory
This step is non-negotiable. Always back up your Active Directory before making any changes to the domain functional level. I once had a scare where I didn’t back up properly before making a change, and it took hours to recover from a minor mistake. Having a solid backup plan gives you peace of mind and ensures that you won’t lose critical data if something goes wrong during the upgrade.
Step 3: Raise the Domain Functional Level Using Active Directory Domains and Trusts
Now, we’re getting to the fun part! Here’s how you raise the domain functional level using Active Directory Domains and Trusts:
- Open Active Directory Domains and Trusts from the Start menu.
- Right-click the domain you want to upgrade and select Properties.
- In the Properties dialog box, look for the Domain Functional Level section.
- Select the new level you want (e.g., Windows Server 2016, Windows Server 2025) and click Raise.
- Confirm the action when prompted.
After completing these steps, the domain functional level will be raised to the level you selected. If you are also planning to raise the forest functional level (which I highly recommend), follow similar steps in the forest settings.
Table 1: Domain Functional Level Compatibility
| Domain Functional Level | Minimum Windows Server Version for Domain Controllers |
|---|---|
| Windows Server 2012 R2 | Windows Server 2012 R2 or higher |
| Windows Server 2016 | Windows Server 2016 or higher |
| Windows Server 2025 | Windows Server 2025 or higher |
Step 4: Test and Monitor the Changes
Once the domain functional level is raised, it’s important to test the changes to ensure everything is working as expected. Check for any replication errors or issues with authentication or security protocols. The changes will take some time to propagate across your domain controllers, so don’t panic if things seem slow at first.
From my experience, testing is where many admins tend to get lax. They assume that everything will work fine without testing, only to run into problems later. Trust me, spend the time to test.
Why Can’t You Just Roll Back the Functional Level?
One of the most crucial things to remember when raising the domain functional level is that it’s irreversible. Once you raise it, there’s no easy way to go back. If you need to revert to an earlier level, you’d have to restore from a backup, which could be a nightmare if you didn’t back up properly.
I learned this the hard way early on in my career. After a functional level upgrade, some of our older applications started to behave strangely. Unfortunately, we had already made the change without backing up properly. So, we had to spend several days fixing things, and since the rollback wasn’t possible, we had to put in extra hours to manually correct issues.
Table 2: Forest Functional Level Changes
| Forest Functional Level | Minimum Windows Server Version for Forest Controllers |
|---|---|
| Windows Server 2012 R2 | Windows Server 2012 R2 or higher |
| Windows Server 2016 | Windows Server 2016 or higher |
| Windows Server 2025 | Windows Server 2025 or higher |
FAQ
1. What is a domain functional level?
A domain functional level determines the features available in your domain, like enhanced security protocols or new authentication methods.
2. Can I raise the domain functional level without upgrading all domain controllers?
No, all domain controllers must be running a compatible version of Windows Server to raise the domain functional level.
3. Is it necessary to raise the forest functional level at the same time?
It’s not required, but it’s often a good idea to raise the forest functional level after the domain functional level is raised to ensure consistency.
4. Can I undo a domain functional level change?
No, changes to the domain functional level are irreversible, so it’s crucial to back up your environment first.
5. How long does it take for the domain functional level change to propagate?
It usually takes some time for the changes to propagate across all domain controllers, so don’t panic if things seem slow initially.
6. What features do I get by raising the domain functional level?
You’ll gain access to new features such as enhanced security protocols, Privileged Access Management, and improved authentication methods.
7. Should I test after raising the domain functional level?
Yes, it’s crucial to test after raising the domain functional level to ensure everything works as expected, especially replication and authentication.
