Core issue
This happens as the ASA does not support transparent authentication.
Resolution
Proxy servers support transparent authentication, but when an ASA is used, the users have to login again. This happens because the ASA does not know about the user credentials.
In order to get the user credentials, the ASA has to communicate to a RADIUS server to confirm the user password.
For more details refer Transparent Firewall Configuration Example
Problem Type
Upgrade or install
Compatibility or Support
Product Family
ASA Hardware & Software
