see this greate article here to expain how SPNs works
Think of an SPN as a “username” used to identify a program that is busy dealing with credentials. And we're only allowed to talk to this program using its “username”. PERIOD. Simple! Yes, that's all an SPN is: a "username". And as with any username, the name itself isn't really that important. It is merely to make identifying a person (or entity) easier to remember to humans. In this particular case, however, there are some naming conventions for this "username". Okay, so what username (SPN) is the right one? And where do we set it? These 2 questions are where all the confusion lies. We split the SPN into 2 parts and occasionally 3 parts: The first part is the “service type” and the second part is the “host name”. And sometimes...