ter's hostname for authentication. Notice that the username Bob-01 appears on the called side, and that there is no reference on the called side to the hostname of the calling side: Calling side: hostname BobsRouter username ISP password 0 SuperSecret1 interface BRI1/0 encapsulation ppp ppp authentication chap callin ppp chap hostname Bob-01 Called side: hostname ISP username Bob-01 password 0 SuperSecret1 interface BRI1/0 encapsulation ppp ppp authentication chap While this configuration works, chances are the only place you'd see it is on a certifi- cation exam. A far more logical approach is to configure the sent username and password in CHAP without having to configure a username that matches the host- name of the remote router: Calling side: hostname BobsRouter interface BRI1/0 Chapter 24: Authentication in Cisco Devices encapsulation ppp ppp authentication chap callin ppp chap hostname Bob-01 ppp chap password 0 SuperSecret1 Called side: hostname ISP username Bob-01 password 0 SuperSecret1 interface BRI1/0 encapsulation ppp ppp authentication chap Using this method, there is no confusion resulting from trying to match the hostnames and passwords in odd ways. Instead, you configure the username and password using the ppp chap interface commands on the calling side. The called side simply has the username and password configured to match. The hostnames, while included for completion, are not necessary in this example (though they are in all the previous CHAP examples). Of all the non-AAA authentication methods available for PPP, this is the most secure, and the easiest to understand. AAA Authentication AAA stands for Authentication, Authorization, and Accounting. Authentication is the process of verifying a user's identity to determine whether the user should be allowed access to a device. Authorization is the act of limiting or permitting access to certain features within the device once a user has been authenticated. Accounting is the recording of actions taken by the user once she has been authenticated an