3Com 3031 Command Reference Manual page 243

ppp chap password
Parameter
One of chap and pap should be selected.
call-in: Authenticates the peer only when the remote user calls in.
default and scheme-name: indicates the authentication algorithm lists configured
by user while authenticating. For detailed description, refer to "AAA section".
Description
Using the ppp authentication-mode command, you can set the local PPP
authentication algorithm for the peer router. Using the undo ppp
authentication-mode command, you can cancel the configuration, i.e. no
authentication.
By default, no authentication is performed.
There are two PPP authentication algorithms:
PAP is a 2-way handshake authentication, which sends the password in plain
text.
CHAP is a 3-way handshake authentication, which sends the password in
encrypted text.
In addition, the defined AAA authentication algorithm list can be used.
Either CHAP or PAP is just an authentication process. The success of the
authentication is decided by AAA, which can authenticate on the basis of the local
authentication database or AAA server.
For the related commands, see local-user, ppp chap user, ppp pap local-user, aaa
authentication-scheme ppp, ppp pap password, and ppp chap password.
Example
Authenticate the peer router by means of PAP on interface Serial0/0/0.
[3Com-Serial1/0/0] ppp authentication-mode pap
Syntax
ppp chap password { simple | cipher } password
undo ppp chap password
View
Interface view
Parameter
password: Password.
simple or cipher: Passwords in plain text or in encrypted text.
PPP and MP Configuration Commands 243