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Old 08-30-10, 12:18 AM   #1
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Join Date: Aug 2010
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Default Linux Tip: How to Configure PPP for dialup for a single machine?

I shall explain how to setup PPP on your Linux machine, so that you can connect to the Internet using an external modem and a Dialup connection. This article explains the setup for the superuser alone (Not normal users).My Setup :

  • My external modem (56kbps) is connected to the Serial Port : ttyS1 (This is COM2 Port under Windows)
  • My ISP (Internet Service Provider) servers send me the following strings for logging in whenever I connect to their servers,
    Login” & “Password“. These exact strings need to be known since they have to be entered in the scripts later on.Other ISP’s may send strings such as “User” and “Pass” or something else. Please note down the strings that you receive when you connect to your ISP. If needed contact your ISP’s helpdesk.
  • Every ISP has generally 2 DNS entries. Actually one is enough but the other one is for backup. This differs for each ISP. For my ISP the DNS entries are ‘′ and ‘′.
    You have find out your ISP’s DNS addresses. My service provider is named (This exact name is also required to be entered in one configuration file).

Procedure :

  • Copy the 2 files ppp-on & ppp-off from the /usr/doc/ppp2.3.10/scripts (exact directory depends on the installation & distribution on your system) to the folder /usr/bin
    You would have to execute these files whenever you want to connect and disconnect from the Internet once the setup is complete. Hence these scripts should have executable rights.
  • Edit the ppp-on script that you have just copied and make the following changes
    Change the telephone no. , username and password to your username, password and your ISP telephone no.
  • Copy the file ppp-on-dialer file from the /usr/doc/ppp2.3.10/scripts to the folder/etc/ppp
    Edit this file to make the following changes
    - Change the connection strings to “ogin” and “assword” (These should be the strings that your ISP sends you when you connect to your ISP, excluding the first letters in both these strings)
    - Change the timeout period (Start of dialing to establishing of final connection) to a sensible value depending on your experience. I have set it to 120 seconds which is substantially more than what is required.
    - Add an extra line after the existing ATZ command. This is to mute the modem once the connection has been made. Else you will hear the signal transfer noises continuously as long as you are connected. (Atleast I heard the sound on mine)OKATM1\
    - Towards the end of the script make a change as follows.. enter your modem port and max speed in the parameters to the chat script. For me it is as follows
    /dev/ttyS1 115200

  • Now edit the /etc/resolv.conf file to show the following
    These lines totally depend on your ISP, so please fill it accordingly.

  • Now the last step is to edit the /etc/ppp/options file and add the following lines. These settings are used whenever a net connection is established on your machine. If you want to know the meaning of each line you can refer to the PPP-How To documentation. There is a sample script with a description for each of these values. I have only selected those values that would be necessary for a normal dial up Internet connection. These should suffice for most dialup users.-detach
    asyncmap 0
    mtu 1500
    Note : This article explains the settings that should be enough for you to connect to the Internet, through the superuser account. For accessing the Internet from user accounts, a few more settings are required. I shall explain those in another tutorial. Though I have heard of a few experiences where even a normal user types ’su’ in a shell window and changes to the superuser mode (this is for home machines where you are both the superuser and the normal user). Once you changed to superuser mode, you might be able to execute ppp-on and ppp-off scripts. This hasn’t really worked at my place, but I have heard quite a few people doing this. I prefer using kppp to do all the work for me.
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