Currently, only one LDAP (Active Directory) server / domain is supportet by XWiki.
Scenario: Each of the following servers (sub1,sub2,sub3) has defined some users. All servers are under a common domain:
XWiki can be configured to let users from one server log in. However, it is not possible for users from other servers to log in. It would be cool if it could be configured like "look up for users from all subdomains / servers under company.com".