Configure Modem Dial-in Debian

Install ppp and mgetty

aptitude install ppp pppconfig mgetty

Configure ppp using pppconfig

create users in /etc/ppp/pap-secrets

# client        server  secret                  IP addresses
dial-in              *       dial-in                       *

Configure /etc/mgetty/mgetty.config. if your modem is connected to /dev/ttyS0. Comment below lines

port ttyS0
  debug 3
  data-only y

Configure /etc/mgetty/dialin.config

add below lines at end of file

all

Check following lines are uncommented in /etc/mgetty/login.config

/AutoPPP/ -     a_ppp   /usr/sbin/pppd auth -chap +pap login debug

Add below lines to /etc/inittab

s0:23:respawn:/sbin/mgetty ttyS0

Now dial from your windows machine. For authentication you can use user dial-in