In the standard Active Directory Connector, it is not possible to specify the branch or sub directory to limit searches to. But the Generic LDAP connector can be configured to do connect to Active Directory and specifying a subdirectory.
Also using Generic LDAP connector makes it possible to set an alias for domain. In a rare situation that a domain called "Internal" can only be connected by Generic LDAP due to naming conflict.
Resolution:
Before setting up UDC, 3 pieces of information are required:
Path
User name
LDAP Filter
It is convenient to use a 3rd party tool called LDAP Admin" to prepare the above 3 pieces of information
Once LDAP Admin is downloaded and run, make a connection to the existing Active Directory. Domain Admin may need to be involved in order to get this step done.
Once connected, go to Edit > Search > Custom
In the Search Window, make sure Path is set to root base. Use the Browse button if necessary.
Create a filter so that only limited number of users are fetched. In the sample below, only 16 users are fetched by using the predefined filter. Please consult Domain Admin about how to construct an LDAP filter.
Now the 3 pieces of information are confirmed and tested. We can start building the Generic LDAP connector.
[VERY IMPORTANT] Before moving forward, confirm if there is any RootAdmin assigned to a domain user in Qlik Sense.
If there is, make sure that user appears in the search result of above filter otherwise it will be marked as inactive and could potentially lock users out from QMC.