These instructions were tested on an out of the box workstation installation of Red Hat 5.2, however they should work on different flavors and versions of Linux as well. Many of the commands that you will need to issue will require you to have root access.

First you will need to find out which COM port your modem uses. If you have Windows9x installed you can determine what COM port your modem is on by doing the following:

1. Double-click "My Computer" icon.
2. Double-click "Control Panel."
3. Double-click "Modems."
4. Left-click on the "Diagnostics" tab at the top.
5. The COM port that your modem is using will be listed next to the name of your modem.

COM ports in Linux are referred to by /dev/ttySX (where X is the device number). The basic way to remember the number following "ttyS" is to subtract one from the number following "COM" in DOS or Windows.

You need to refer to that device using /dev/modem by making a symbolic link from /dev/ttySX ('X' representing whatever that number is) to /dev/modem. You would type the following if your modem was on COM2:

ln -s /dev/ttyS1 /dev/modem

If you are using a 56k modem you may want to add the following line into your /etc/rc.d/rc.local file so that your port will use 57.6kb instead of 38.4kb:

setserial /etc/modem spd_hi

Now you will need to create/edit several files. Make sure that you don't copy these files word for word without reading the comments first, some of the files will need information regarding your dialup account and your computer configuration.

/etc/resolv.conf

search qis.net
nameserver 209.150.96.20
nameserver 209.150.96.21

/etc/ppp/pap-secrets

In the /etc/ppp/pap-secrets file you will want to replace "your username," and "your password" with your actual username and password.

# Secrets for authentication using PAP
# client	server  secret                  IP addresses
your username	*	your password

/etc/ppp/options

In the /etc/ppp/options file you will want to replace "your username" with your actual username.

lock
name your username

/etc/ppp/ppp-on

In the /etc/ppp/ppp-on script you will want to replace the telephone number, and if you have a 56k modem you will want to change the port speed from 38400 to 57600.

#!/bin/sh
#
# Script to initiate a ppp connection. This is the first part of the
# pair of scripts. This is not a secure pair of scripts as the codes
# are visible with the 'ps' command.  However, it is simple.
#
# These are the parameters. Change as needed.
TELEPHONE=555-1212	# The telephone number for the connection
LOCAL_IP=0.0.0.0	# Local IP address if known. Dynamic = 0.0.0.0
REMOTE_IP=0.0.0.0	# Remote IP address if desired. Normally 0.0.0.0
NETMASK=255.255.255.0	# The proper netmask if needed
#
# Export them so that they will be available at 'ppp-on-dialer' time.
export TELEPHONE
#
# This is the location of the script which dials the phone and logs
# in.  Please use the absolute file name as the $PATH variable is not
# used on the connect option.  (To do so on a 'root' account would be
# a security hole so don't ask.)
#
DIALER_SCRIPT=/etc/ppp/ppp-on-dialer
#
# Initiate the connection
#
# I put most of the common options on this command. Please, don't
# forget the 'lock' option or some programs such as mgetty will not
# work. The asyncmap and escape will permit the PPP link to work with
# a telnet or rlogin connection. You are welcome to make any changes
# as desired. Don't use the 'defaultroute' option if you currently
# have a default route to an ethernet gateway.
#
exec /usr/sbin/pppd debug lock modem crtscts /dev/modem 38400 \
        asyncmap 20A0000 escape FF kdebug 0 $LOCAL_IP:$REMOTE_IP \
        noipdefault netmask $NETMASK defaultroute connect $DIALER_SCRIPT

/etc/ppp/ppp-on-dialer

In the /etc/ppp/ppp-on-dialer script you may need to add the init string for you modem on the line that has AT in quotes. 

#!/bin/sh
#
# This is part 2 of the ppp-on script. It will perform the connection
# protocol for the desired connection.
#
exec chat -v                                            \
        TIMEOUT         3                               \
        ABORT           '\nBUSY\r'                      \
        ABORT           '\nNO ANSWER\r'                 \
        ABORT           '\nRINGING\r\n\r\nRINGING\r'    \
        ''              \r"AT"                          \
        'OK-+++\c-OK'   ATH0                            \
        TIMEOUT         30                              \
        OK              ATDT$TELEPHONE                  \
        CONNECT         ''                              

Now that you have created all of the required configuration files you can initiate a dialup connection by typing the command:

/etc/ppp/ppp-on

You can monitor the progress of your dial-up connection by typing:

tail -f /var/log/messages

The results of the connection should look similar to this:

Aug 13 08:13:49 mycomputer pppd[5191]: pppd 2.3.5 started by root, uid 0
Aug 13 08:13:50 mycomputer chat[5192]: timeout set to 3 seconds
Aug 13 08:13:50 mycomputer chat[5192]: abort on (\nBUSY\r)
Aug 13 08:13:50 mycomputer chat[5192]: abort on (\nNO ANSWER\r)
Aug 13 08:13:50 mycomputer chat[5192]: abort on (\nRINGING\r\n\r\nRINGING\r)
Aug 13 08:13:50 mycomputer chat[5192]: send (rAT^M)
Aug 13 08:13:50 mycomputer chat[5192]: expect (OK)
Aug 13 08:13:50 mycomputer chat[5192]: rAT^M^M
Aug 13 08:13:50 mycomputer chat[5192]: OK
Aug 13 08:13:50 mycomputer chat[5192]:  -- got it
Aug 13 08:13:50 mycomputer chat[5192]: send (ATH0^M)
Aug 13 08:13:50 mycomputer chat[5192]: timeout set to 30 seconds
Aug 13 08:13:50 mycomputer chat[5192]: expect (OK)
Aug 13 08:13:50 mycomputer chat[5192]: ^M
Aug 13 08:13:51 mycomputer chat[5192]: ATH0^M^M
Aug 13 08:13:51 mycomputer chat[5192]: OK
Aug 13 08:13:51 mycomputer chat[5192]:  -- got it
Aug 13 08:13:51 mycomputer chat[5192]: send (ATDT*70,4108486493^M)
Aug 13 08:13:51 mycomputer chat[5192]: expect (CONNECT)
Aug 13 08:13:51 mycomputer chat[5192]: ^M
Aug 13 08:14:11 mycomputer chat[5192]: ATDT*70,4108486493^M^M
Aug 13 08:14:11 mycomputer chat[5192]: CONNECT
Aug 13 08:14:11 mycomputer chat[5192]:  -- got it
Aug 13 08:14:11 mycomputer chat[5192]: send (^M)
Aug 13 08:14:11 mycomputer pppd[5191]: Serial connection established.
Aug 13 08:14:12 mycomputer pppd[5191]: Using interface ppp0
Aug 13 08:14:12 mycomputer pppd[5191]: Connect: ppp0 <--> /dev/modem
Aug 13 08:14:18 mycomputer pppd[5191]: Remote message: Login Succeeded
Aug 13 08:14:19 mycomputer pppd[5191]: local  IP address 209.150.96.155
Aug 13 08:14:19 mycomputer pppd[5191]: remote IP address 209.150.96.2

When you are done monitoring your connection you can press at the same time to take to back to the prompt.

You can also verify that you have a ppp connection by typing:

ifconfig

The results of the command should display interfaces that looks similar to this (depending on your configuration there may be other interfaces listed such as eth0):

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:3924  Metric:1
          RX packets:106 errors:0 dropped:0 overruns:0 frame:0
          TX packets:106 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0

ppp0      Link encap:Point-to-Point Protocol
          inet addr:209.150.96.155  P-t-P:209.150.96.2  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:1372 errors:5 dropped:0 overruns:0 frame:5
          TX packets:1435 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:10

When you are ready to disconnect from the internet type the command:

/etc/ppp/ppp-off

If you follow these instructions and you are still unable to connect, you may want to read the Linux PPP-HOWTO at the Linux Documentation Project. The documentation and example scripts that come with the ppp can also be very helpful.