Loop Back Issue in Sharepoint

Issue

Browse a SharePoint Web Application which uses a fully qualified domain name from a WFE in the farm you will get a 401.1. This error code means there is a problem with the user credentials but nothing to do with invalid credentials.

Windows Server 2003 SP1 introduced a loopback security check. By default this feature enabled in Windows Server 2008. The feature prevents access to a web application using a fully qualified domain name (FQDN) if an attempt to access it takes place from a machine that hosts that application and shows a 401.1 Access Denied from the web server and a logon failure in the event log.

How to Solve this

You need to create a DWORD registry key called DisableLoopbackCheck and set it to 1.

Steps

1. Start -> Run, type regedit

2. Go to following registry key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa

3. Add a new DWORD Value in LSA key.

4. Type DisableLoopbackCheck, and then press ENTER.

5. Modify DisableLoopbackCheck and set Value to 1.

6. Exit Registry Editor

7. Restart your computer.