I continued to run into issues with Kerberos and error message like Login failed for user ‘NT AUTHORITY\ANONYMOUS LOGON’ when using SharePoint Reporting Services and a SQL DB that I was reporting on a different server.
When configuring Kerberos with previous SQL versions and SharePoint it was easy to set the delegation to “Trust this user for delegation to any service”. after setting SPNs you would be good to go.
However, with SSRS 2012 things have changed and SharePoint now uses the Claims To Windows Service to get authenticated correctly. I had it half way right and the fix was to add “trust this user for delegation to specified services only” on both the Claims To Windows Account and the SharePoint SSRS 2012 account. I found a sweet video on what needs to be done here: