Restrictions and guidelines for specifying a portal authentication domain
The device selects the authentication domain for a portal user in this order:
ISP domain specified for the interface.
ISP domain carried in the username.
System default ISP domain.
If the chosen domain does not exist on the device, the device searches for the ISP domain configured to accommodate users assigned to nonexistent domains. If no such ISP domain is configured, user authentication fails. For information about ISP domains, see "Configuring AAA."