There are several different reasons why you would have multiple Active Directory forests and there are several different deployment topologies. Common models include an account-resource deployment and GAL sync’ed forests after a merger & acquisition. But even if there are pure models, hybrid models are common as well. The default configuration in Azure AD Connect sync does not assume any particular model but depending on how user matching was selected in the installation guide, different behaviors can be observed.
In this topic, we will go through how the default configuration behaves in certain topologies. We will go through the configuration and the Synchronization Rules Editor can be used to look at the configuration.
There are a few general rules the configuration assumes:
- Regardless of which order we import from the source Active Directories, the end result should always be the same.
- An active account will always contribute sign-in information, including userPrincipalName and sourceAnchor.
- A disabled account will contribute userPrincipalName and sourceAnchor, unless it is a linked mailbox, if there is no active account to be found.
- An account with a linked mailbox will never be used for userPrincipalName and sourceAnchor. It is assumed that an active account will be found later.
- A contact object might be provisioned to Azure AD as a contact or as a user. You don’t really know until all source Active Directory forests have been processed.
Having contacts representing a user in a different forest is common after a merger & acquisition where a GALSync solution is bridging two or more Exchange forests. The contact object is always joining from the connector space to the metaverse using the mail attribute. If there is already a contact object or user object with the same mail address, the objects are joined together. This is configured in the rule In from AD – Contact Join. There is also a rule named In from AD – Contact Common with an attribute flow to the metaverse attribute sourceObjectType with the constant Contact. This rule has very low precedence so if any user object is joined to the same metaverse object, then the rule In from AD – User Common will contribute the value User to this attribute. With this rule, this attribute will have the value Contact if no user has been joined and the value User if at least one user has been found.
For provisioning an object to Azure AD, the outbound rule Out to AAD – Contact Join will create a contact object if the metaverse attribute sourceObjectType is set to Contact. If this attribute is set to User, then the rule Out to AAD – User Join will create a user object instead. It is possible that an object is promoted from Contact to User when more source Active Directories are imported and synchronized.
For example, in a GALSync topology we will find contact objects for everyone in the second forest when we import the first forest. This will stage new contact objects in the AAD Connector. When we later import and synchronize the second forest, we will find the real users and join them to the existing metaverse objects. We will then delete the contact object in AAD and create a new user object instead.
If you have a topology where users are represented as contacts, make sure you select to match users on the mail attribute in the installation guide. If you select another option, then you will have an order dependent configuration. Contact objects will always join on the mail attribute, but user objects will only join on the mail attribute if this option was selected in the installation guide. You could then end up with two different objects in the metaverse with the same mail attribute if the contact object was imported before the user object. During export to Azure AD, an error will be thrown. This behavior is by design and would indicate bad data or that the topology was not correctly identified during the installation.
Disabled accounts are synchronized as well to Azure AD. Disabled accounts are common to represent resources in Exchange, for example conference rooms. The exception is users with a linked mailbox; as previously mentioned, these will never provision an account to Azure AD.
The assumption is that if a disabled user account is found, then we will not find another active account later and the object is provisioned to Azure AD with the userPrincipalName and sourceAnchor found. In case another active account will join to the same metaverse object, then its userPrincipalName and sourceAnchor will be used.
When an object has been exported to Azure AD then it is not allowed to change the sourceAnchor anymore. When the object has been exported the metaverse attribute cloudSourceAnchor is set with the sourceAnchor value accepted by Azure AD. If sourceAnchor is changed and not match cloudSourceAnchor, the rule Out to AAD – User Join will throw the error sourceAnchor attribute has changed. In this case, the configuration or data must be corrected so the same sourceAnchor is present in the metaverse again before the object can be synchronized again.