When you, or a thin client, tries to log onto a Windows server using the IP address as a user name, you receive:
The system cannot log you on due to the following error:
The specified target is unknown or unreachable
This behavior occurs because the Kerberos client included with Windows Server 2003 and Windows 2000 Server does NOT allow interactive logon when you use an IP address for the user name.
To workaround this behavior, use the UPN format (User Principal Name), like [email protected],
where oct1.oct2.oct3.oct4 is your IP address.