While Active Directory has served many enterprises for many years, it's on-premises roots can hold back some organizations that have cloud ambitions.
Microsoft Entra ID, formerly Azure Active Directory, is not a direct replacement for on-premises Active Directory due to feature gaps and alternative ways to perform similar identity and access management tasks. But for some organizations, a move to Microsoft Entra ID makes sense.
What are the benefits of a migration to Microsoft Entra ID?
Even though replacing an Active Directory environment is not a good option for every organization, there are several benefits to migrating to Microsoft Entra ID. For example, numerous cloud services use Microsoft Entra ID as an identity management provider.
This is important because as organizations adopt an ever-increasing number of cloud applications and cloud services, it becomes less practical to manage each one individually. Microsoft Entra ID acts as a centralized identity management provider to streamline access to a variety of cloud-based resources.
Microsoft Entra ID scales more easily than an on-premises Active Directory environment. Scaling Active Directory usually means adding more domain controllers, which increases the management and maintenance overhead. As a serverless, managed service, Microsoft Entra ID automatically scales so the organization does not need to deal with the hassles of deploying domain controllers.
Microsoft Entra ID is generally more secure than the Active Directory. Most organizations do not take advantage of all the available Windows Server security mechanisms that would allow them to harden the Active Directory to the greatest extent possible. Microsoft Entra ID was created with security at the forefront of the design process.
During the planning stage, you might discover your organization cannot rely solely on Microsoft Entra ID for identity and access control. There are other options, such as a hybrid environment that uses Microsoft Entra Connect to synchronize your Active Directory to Microsoft Entra ID. Another option is to create parallel environments, using Microsoft Entra ID for cloud-based services but maintaining Active Directory for resources with a dependency that cannot use Microsoft Entra ID.
How to plan a migration to Microsoft Entra ID
Every migration to Microsoft Entra ID is different because each environment has its own dependencies and requirements. As such, it's important to develop a thorough plan for the migration process.
The first thing to consider is deciding which objects need to be migrated. Some Active Directory objects, such as user objects, will almost always be included in a migration. However, there are other object types that will likely become irrelevant or that might even be unsupported in Microsoft Entra ID. For example, you won't need site objects in a Microsoft Entra ID environment. Likewise, there might be some Active Directory groups that will no longer be relevant that you can delete.
As you plan for the Microsoft Entra ID migration, consider how you will handle DNS services. Active Directory has a dependency on DNS and so many domain controllers double as DNS servers. If you phase out your on-premises Active Directory environment, then your domain controllers might be decommissioned. You might need to deploy standalone DNS servers or adopt cloud-based DNS servers. If you decide to maintain on-premises DNS servers, then check whether your migration to Microsoft Entra ID will require changing or removing certain DNS records.
It's also important to consider the order to migrate objects. This might not be a problem for smaller organizations, but larger organizations probably won't be able to migrate everything at once, so a migration plan that minimizes any disruptions for your users is crucial. Microsoft offers guidance for migrating applications that can help with your planning process.
Once you have developed a migration plan, consider how you can validate that plan, such as setting up a test environment and performing a trial migration.
Check that the Active Directory environment is healthy and up to date. Part of this process might involve updating domain controllers, raising functional levels and ensuring the Active Directory adheres to Microsoft's best practices.
Most organizations also establish a hybrid Active Directory environment, which involves using Microsoft Entra Connect to synchronize the Active Directory to Microsoft Entra ID. Verify that the sync rules are configured properly based on your organization's requirements.
Execute and check object synchronization
Once you have synchronized your Active Directory to Microsoft Entra ID, it's important to verify that the synchronization is working as intended. Make sure that the correct objects have been synchronized and there are no errors in the logs. It's critically important to address any synchronization problems before you move to the next stage of the migration.
What are some post-migration tasks to perform?
After a successful synchronization, configure your applications to use Microsoft Entra ID for authentication and access control.
With the migration complete, you can start the process to shut down the Active Directory environment. Because deprovisioning could cause an unforeseen problem, it's best to power down the domain controllers before removing them until you are confident everything is working properly and there is no further need for the legacy domain controllers.
Brien Posey is a 15-time Microsoft MVP with two decades of IT experience. He has served as a lead network engineer for the U.S. Department of Defense and as a network administrator for some of the largest insurance companies in America.