In the SharePoint install document I have it says,
If you use a domain user account for the SQL Server service account, you must make sure that a valid service principal name (SPN) for that account and instance of SQL Server on their database server exists in their environment. This is the case regardless of whether you use NTLM or Kerberos authentication for Office SharePoint Server 2007.
You must configure the SPN for that account in the domain using the Setspn.exe command-line tool. Setspn.exe is installed by default on computers running Windows Server 2008. Run the following command on a computer that is joined to the same domain as the user/service account.
setspn -a <http/<farmclusterdnsname> <serviceaccountname> What should the parameters be in this case?
I guess the serviceaccountname would be ‘domain\username’ not sure what the first parameter should be though.
This is the technet link for SetSPN.
The syntax would look something like the following:
or
Try and think of it this way: You want to register the owner of the http service for http://www.mywebsite.com to the domain\serviceaccountname directory object. This spn entry allows the authentication tickets to be encrypted with the password registered for the owner (serviceaccountname) of the service (http) on the registration name (www.mywebsite.com).
After you have added the SPN entry you can verify the results by using the ‘SetSPN -l’ on the owner (serviceaccountname) by executing the command:
One thing to point out. You can only have one owner for the service (http) and the registration name (www.mywebsite.com) in the environment. It might be possible to accidentially end up with more than one.
Use the SetSPN -l option to lookup the registration entries for the computer object where SharePoint is installed to make sure there isn’t already an entry: ex.
You can read much more about how SPN works at the Microsoft TechNet web site.