Ryan Bushnell posted an excellent walkthrough of KCD with SSRS 2012 and SP2013! (That’s Kerberos Constrained Delegation; SQL Server Reporting Services; SharePoint 2013)
To do this configuration Kerberos with constrained delegation is required and often this is the most tricky and unclearly documented piece. In this post I hope to provide some insight into the steps to configure these pieces.
Yep; it’s a topic with many moving parts, but surprisingly straightforward when you get your head around it. Ryan wins further points by using SetSPN -S (from Windows Server 2008 and later) instead of the older -A switch (remember to update that documentation)!
It’s a very clear illustration of a very common scenario, and well worth digesting if you’re likely to have to set it up.
Much more at the original post.