Import Portal Users - authenticate against r3

We're in the process of replacing our Portal (EP) with new machines.

Becasue we use the backend r3 for authenitication, when we export then import the users on the portal will this have any effect on the backend r3 user details, or does the import only update the portal accounts?

I believe it has no effect on the back-end just hoping to get confirmation.

Thanks

Ian