Modifying Name Suffix Routing Settings

Applies To: Windows Server 2008, Windows Server 2008 R2

Name suffix routing is a mechanism for managing how authentication requests are routed across Windows Server 2008 forests and Windows Server 2003 forests that are joined by forest trusts. To simplify the administration of authentication requests, when a forest trust is created, all unique name suffixes are routed by default. A unique name suffix is a name suffix within a forest, such as a user principal name (UPN) suffix, Service Principal Name (SPN) suffix, or Domain Name System (DNS) forest or domain tree name, that is not subordinate to any other name suffix. For example, the DNS forest name is a unique name suffix within the forest.

All names that are subordinate to unique name suffixes are routed implicitly. For example, if your forest uses as a unique name suffix, authentication requests for all child domains of ( will be routed because the child domains are part of the name suffix. Child names are displayed in the Active Directory Domains and Trusts snap-in. If you want to exclude members of a child domain from authenticating in the specified forest, you can disable name suffix routing for that name. You can also disable routing for the forest name itself, if necessary.

For more information about name suffix routing, see Routing name suffixes across forests (


You cannot enable a name suffix that is the same as another name in the routing list. If the conflict is with a local UPN name suffix, you must remove the local UPN name suffix from the list before you can enable the routing name. If the conflict is with a name that is claimed by another trust partner, you must disable the name in the other trust before it can be enabled for this trust.

Task requirements

You can use either of the following tools to perform the procedures for this task:

  • Active Directory Domains and Trusts

  • Netdom.exe

For more information about using the Netdom command-line tool to modify name suffix routing, see Netdom Overview (

To complete this task, you can perform the following procedures: