Machine names and SPNs

A Service Principle Name (SPN) is the name by which a client uniquely identifies an instance of a service. By default your IIS machine has SPNs for its hostname, such as myServer, and its Fully Qualified Domain Name (FQDN), such as myServer.branch.example.com.

If the proxy machine is accessed by a name other than either of these, such as myServer.example.com, otherName.company.com, or its IP address, then Active Directory authentication will not work. Your choices are:

• Access the machine using either its host name or FQDN.

• Register an additional SPN for the proxy machine on the domain controller.

SPNs can be viewed and changed with the setspn.exe tool, which Microsoft provides as part of its Windows 2003 Support Tools. This package is available on the Windows 2003 CD, or, at the time of writing, at http://go.microsoft.com/fwlink/?LinkId=100114.