SPN checklist for Kerberos authentication with IIS 7.0/7.5

This post is more about the confusion that may arise around SPNs for setting up Kerberos authentication in IIS 7.0. IIS 7.0 has a new Kernel-mode authentication feature using which the ticket for the requested service is decrypted using Machine account (Local system) of the IIS server. It no longer depends upon the application pool

IIS 7.0 Kernel Mode Authentication by default

In Windows Server 2008, kernel mode authentication runs under the machine account, but Office Communications Server 2007 R2 runs under a user account. As a result, Kerberos service ticket decryption fails if kernel mode authentication is enabled. If you install and activate Office Communications Server 2007 R2 on a computer running the Windows Server 2008