Method of Authentication
User authentication for auth-proxy can be performed using one of four methods: HTTP, Secure HTTP (HTTPS), Telnet, or FTP. HTTPS support for auth-proxy was first introduced in IOS version 12.2(11)YU, and was first integrated in version 12.2(15)T. However, FTP and Telnet support was introduced in IOS version 12.3(1). The mechanism of auth-proxy is the same regardless of methods for authentication being used. For HTTP, TELNET or FTP authentication, username and password goes in clear text from client to the router. If you want to encrypt the packets, you need to configure HTTPS. Ensure that the Cisco IOS image supports crypto (*k9) to be able to configure HTTPS.