Two or more moderately complex Active Directory (AD) “forests” can be linked so that users in one forest can easily access resources in the other forest. In this case involving fictitious example companies, ABC Limited has acquired XYZ Corporation.

Both firms were using Windows Server 2003–based AD forests before the acquisition. ABC is a Canadian firm with a U.S. subsidiary. ABC has three domains (represented by triangles) in its tree-a root domain, abc.com, and two subsidiaries. All are linked by native AD two-way transitive trusts (represented by solid connecting lines). Its U.S. subsidiary, abcus.com, has a separate tree consisting of a main domain and a separate domain for its software development group. This tree and the abc.com tree mutually trust each other (also using native AD two-way transitive trusts), but each tree has a different namespace. Because of the transitive trusts, all domains in the ABC forest completely trust each other and share a common schema and global catalog.