The request failed with HTTP Status 401: Unauthorized

Error Message

When the connect button is clicked while adding a map service in ArcGIS for AutoCAD, the following error occurs:"The request failed with HTTP Status 401: Unauthorized".

Cause

Only Anonymous Authentication is permitted with ArcGIS for AutoCAD, build 200.

Solution or Workaround

• When connecting to services that are not secured by ArcGIS Server: Anonymous Authentication must be granted to the services directory in Internet Information Services (IIS).
  
  For IIS 7 (Windows 2008 Server and Vista):
  1. In Internet Information Services (IIS) Manager, expand {HOSTNAME} > Sites > Default Web Site > {Instance Name (ArcGIS)}.
  2. Select the services directory.
  3. Double-click Authentication.
  4. Right-click Anonymous Authentication and select Enable.
  
  For IIS 5 and 6 (Windows XP and Windows 2003 Server):
  1. In Internet Information Services (IIS) Manager, expand {HOSTNAME} > Web Sites > Default Web Site > {Instance Name (ArcGIS)}.
  2. Right-click the Services directory and select Properties.
  3. On the Directory Security tab, under Anonymous access and authentication control, click Edit.
  4. Make sure Anonymous Access is checked on.
  5. Click OK to close the dialog boxes and apply the changes.
• When connecting to services secured by ArcGIS Server: See the information in the Knowledge Base article titled, "Error when adding secure service to ArcGIS for AutoCAD", in the Related Information section below.