Connecting to R/3 system from External facing portal

Hi folks,

We have implemented an external facing portal where all the users are been stored in a separate CRM system. Hence for checking whether the user id and password is correct we are using a CRM BAPI call. For making a CRM BAPI call we have created an alias from the portal end to the CRM system and the authentication type which we choose was SAP Logon ticket. Now my question is:

1. Will the SAP logon ticket will be created automatically or not as the users are not stored at the portal but in CRM. If it is not going to create a SAP logon ticket then how this can be achieved.

Your thoughts are highly appreciated.

Regards,

Ponraj M