Authentication is the process of verifying that a user is who he or she claims to be. The UNIX login sequence is a simple form of authentication:
The login command prompts the user for a name and password.
login then attempts to authenticate the user by looking up the typed user name and password in the password database.
If the database contains the user name and password, then the user is authenticated and given access to the system. If the database does not contain the user name and password, the user is denied access to the system.
By default, Solaris PPP 4.0 does not demand authentication on machines that do not have a default route specified. Thus, a local machine without a default route does not authenticate remote callers. Conversely, if a machine does have a default route defined, the machine always authenticates remote callers.
You might use PPP authentication protocols to verify the identity of callers who are trying to set up a PPP link to your machine. Conversely, you must configure PPP authentication information if your local machine must call peers that authenticate callers.