set SPN on SQL cluster
To create a SPN for a SQL FCI, use the FQDN of the FCI instance. For example, if the FCI name is "SQLFCI1" on the contoso domain and it listens on port 22000 with domain account SQLSvcAcct then the spn would be: setspn -s MSSQLSvc/SQLFCI1.contoso.com:22000 Contoso\SQLSvcAcct

If you don't want to deal with doing this by hand there is a great tool provided by Microsoft for this.