Windows Login is used. If you run a search at the Microsoft Sharepoint within the result list appear following error message:
"Login failed for user NT AUTHORITY\IUSR"
Anonymous user is used, somewhere on the way from Sharepoint to the SearchFederationServer.
The websites and the website of the Webservices have Anonymous and Trusted Login enabled. Deactivate the anonymous authentification.
You want to create a new web instance but it will not appear in the context menu. And the option "Create New Webinstance" is greyed out at "Edit" .
The modul "Connect to MFP" is not installed.
You need to install the missing modul to that machine where the IIS and the "Web Modules" are installed.