Cisco Certification Introduction To ISDN Part IV
In part III of this ISDN primer, we learned that PPP has two main methods of authentication that Cisco certification candidates need to know how to configure: PAP and CHAP.
PAP has very few advantages over CHAP. PAP passwords are carried over the line in clear-text, which in today's world is a very bad idea. PAP configuration also requires additional configuration with the "ppp pap sent-username" command, so anyone who can see your running configuration can also see the PAP password.
The only advantage PAP has over CHAP is a slim one. With PAP, a different password can be used by the each of the routers involved in the authentication. CHAP requires that the password be the same. Why? We'll see...
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