ArcGIS Server services URL 'https://<server.domain>/<server web adaptor instance>' cannot be validated against 'https://<server.domain>/<server web adaptor instance>/rest/info'. If the service URL is a proxy URL verify it is accessible to clients

Error Message

Attempting to validate ArcGIS Server from the portal admin page fails, and the following error messages are returned:

Error:
ArcGIS Server services URL 'https://<server.domain>/<server web adaptor instance>' cannot be validated against 'https://<server.domain>/<server web adaptor instance>/rest/info'. If the service URL is a proxy URL verify it is accessible to clients.

Error:   
Error: java.lang.Exception: Server returned HTTP status code 401. Requested URL: https://<server.domain>/<server web adaptor instance>/admin/info?f=json&token=<token value>

Cause

In a federated portal environment with Integrated Windows Authentication (IWA), Portal for ArcGIS controls the token generation when accessing ArcGIS Server services. In this case, the authentication on the server web adaptor instance and the portal web adaptor instance under Internet Information Services (IIS) Manager shows IWA as enabled on both Portal for ArcGIS and ArcGIS Server. IWA must be disabled on the ArcGIS Server site. This is necessary so the site is free to federate with the portal, and read the portal's users and roles from IWA.

Solution or Workaround

Change the authentication method settings for the ArcGIS Server web adaptor using Internet Information Services (IIS) Manager.

1. On the machine, navigate to Start > Control Panel > Administrative Tools, and click Internet Information Services Manager to open IIS Manager.
2. In the Connections window, navigate to Sites > Default Web Site > server, and click Authentication under IIS.
3. Right-click Anonymous Authentication, and click Enable.
4. Right-click Windows Authentication, and click Disable.

5. Validate ArcGIS Server using the ArcGIS REST API. Refer to ArcGIS REST API: Validate Server for more information.