Trust Relation Types in Windows 2003 and 2008 Server

Parent-child trust

This trust is implicitly created when we add a new child domain to a tree. This trust is a two-way and transitive in nature.

Tree-root Trust

This trust is implicitly established when we add a new tree root domain to a forest. This trust is two-way and transitive in nature.

Shortcut Trust

This trust is created to improve user logon times between two domains in a forest. This trust is created explicitly, transitive and can be one-way or two-way.

As you can see in the above diagram, one-way trust is created from techpeoples.net to asia.microsoft.com so that users in asia.microsoft.com can logon to techpeoples.net domain, but not vice-versa. In other scenario, two way trusts is created between usa.techpeoples.net and europe.microsoft.com so that users in each domain can logon to other domain, two-way trust.

External Trust

External trust is created between two different forests or between a Windows Server 2003 domain and Windows NT 4 domain. This trust is explicitly created, non-transitive in nature and can be one-way or two-way.

 

As you can see in the above diagram, one-way trust is created from techpeoples.net to asia.microsoft.com so that users in asia.microsoft.com can logon to techpeoples.net domain, but not vice-versa. In other scenario, two way trusts is created between usa.techpeoples.net and europe.microsoft.com so that users in each domain can logon to other domain, two-way trust.

Realm Trust

Realm trust is created between a Windows Server 2008 and non-windows Kerberos realm. This trust us explicitly created, non-transitive and can be one-way or two-way.

Forest Trust

 Forest trust is created between two forest root domains. Trust is explicitly transitive in nature and can be one-way or two-way.

 

As you can see in the above diagram, a two-way trust is created between two different forests.