SPN for external domain name

Hi everybody,

I need help with SPN for my PBIRS. I have domain account for my RS service and it has 2 SPN:

setspn -L service.pbi
Registered ServicePrincipalNames for CN=service.pbi,OU=Services,DC=domain,DC=local:
HTTP/srv-powerbi.domain.local
HTTP/srv-powerbi

And kerberos works fine. But I want to use my external domain name, like bi.domain.com.

I've tried to add SPN like HTTP/bi.domain.com for my service account but it doesn't help me.

Maybe anyone has expirience with this case and can help me?