Log in to the dial-in server as superuser.
Modify the /etc/ppp/options file.
Add the options that are shown in bold for CHAP support.
# cat /etc/ppp/options lock nodefaultroute name CallServe auth
Create the remaining PPP configuration files to support the trusted callers.
To configure CHAP authentication credentials for trusted callers, refer to How to Create a CHAP Credentials Database (Dial-in Server).