Windows Authentication not working in IIS on Windows Server 2003

[Soggy Bottom]

I am getting an error "HTTP 401.1 - Unauthorized: Logon Failed". I have installed window Server 2003 SP1 and configure IIS site. When i use that site to use host header the error occur which won't allowed me to login.Any recommendations and suggestions are appreciated.

[Calvin K]

This issue occurs if you install Microsoft Windows XP Service Pack 2 (SP2) or Microsoft Windows Server 2003 Service Pack 1 (SP1). Windows XP SP2 and Windows Server 2003 SP1 include a loopback check security feature that is designed to help prevent reflection attacks on your computer. Therefore, authentication fails if the FQDN or the custom host header that you use does not match the local computer name.

[jesse]

The problem can be solve by disabling loopback on the server. the method for disabling loopback is given below :

First open regedit > HKLM\System\CurrentControlSet\Control\Lsa > In that registry create a new DWORD value called DisableLoopbackCheck and assign the value of 1 then restart you computer.

[Wynn]

• Click Start, click Run, type regedit, and then click OK.
• In Registry Editor, locate and then click the following registry key:
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
• Right-click Lsa, point to New, and then click DWORD Value.
• Type DisableLoopbackCheck, and then press ENTER.
• Right-click DisableLoopbackCheck, and then click Modify.
• In the Value data box, type 1, and then click OK.
• Quit Registry Editor, and then restart your computer.