Linux PPP Configuration

Red-Hat 6.0 Linuxconf

This document describes configuring a PPP connection to Datasync with the linuxconf tool supplied with Redhat Linux 6.0. Earlier versions should be similar though perhaps not exactly so.

You must have the linuxconf and ppp packages installed. Verify this with rpm -q linuxconf and rpm -q ppp. Your kernel must also support ppp. This should be true with any Redhat-supplied kernel.

As the superuser (root), run linuxconf in a console or xterm window. Linuxconf uses a series of expanding and collapsing menus. If a menu is collapsed, it has a plus sign (+) in front of it. If a menu is expanded, it has a minus sign (-) in front. To expand a collapsed menu, use the up/down arrows to highlight the desired selection and press ENTER.

Expand the menu labeled Config, then Networking under it, then Client Tasks under it.

Now select PPP/SLIP/PLIP. You will get a dialog labeled PPP/Slip/Plip configurations with a list of available interfaces.

You may have one named ppp0 already configured. If so, skip down to Configuring the PPP Interface.

Adding a new PPP Interface

Use TAB to get to the Add button and press ENTER. For the type of interface, select PPP, then press Accept. Now you can configure the ppp0 interface. Use these values:

  • Phone number: enter your local Datasync dialup number. Find it here if you don't know it.
  • Modem port: Usually this is /dev/modem, if you configured the modem at install time. Otherwise use /dev/ttyS0 if your modem is on COM1, /dev/ttyS1 for COM2, /dev/ttyS2 for COM3, or /dev/ttyS3 for COM4.
  • Use PAP Authentication: Yes, check this box by pressing SPACE while it's highlighted.
  • Login name: your Datasync login ID.
  • Password: you Datasync password.

Now press Accept to add the new ppp interface. You will now go back to PPP/Slip/Plip configurations.

Configuring the PPP Interface

Highlight the ppp0 interface and press ENTER. These items are of most interest:

  • Allow any user (de)activate the interface: This allows you to connect and disconnect as a non-root user, which is generally a good idea.
  • Modem port: set at interface addition time; see above for possible values.
  • Modem init string: usually this is ATZ, but you may need additional commands here depending on your modem and line quality. Append any additional strings you need to the ATZ.
  • Phone number: set at interface addition time; find it here if you don't know it.
  • In the Chat section, you should NOT have any Expect/Send pairs for the login and password. On some of our servers this will prevent you from logging in. There may a few other things here like TIMEOUT, which is OK.
  • Under Networking, Activate interface at boot time should not be checked. Set Default Route should be checked.
  • Finally, under PAP, the Username and Secret are your Datasync login ID and Password.

Use the Accept button to save any changes.

Configuring DNS

You must also configure the DNS servers or you won't be able to resolve any hostnames. This may also be done in linuxconf under Client Tasks. Select Name Server Specification (DNS).

In the Resolver configuration dialog, make sure these are set:

  • default domain:
  • nameserver 1:
  • nameserver 2:

Logging in and out

Now you should be ready to log in. If the interface was configured to allow any user to activate it, you need not be root to do this. The command to connect is:

ifup ppp0

If the command ifup was not found, try /sbin/ifup ppp0.

Within a few seconds you, should hear the modem dial. To follow the progress of the connection, you can run:

tail -f /var/log/messages

which will have to be done as root. Once you see pppd log the local and remote IP addresses, you're in. Otherwise there will be diagnostic information to help determine why the login failed.

To logout, use the command:

ifdown ppp0

or /sbin/ifdown ppp0. The modem should hang up.

Configuring additional PPP interfaces

By following the same steps described above, you can add additional ppp interfaces, which will be named ppp1, ppp2, etc. For example, you may wish to set up ppp1 to use a second dialup number or to log in as a different user.

The use the alternate configuration, simply use its name instead of ppp0 in the calls to ifup and ifdown, e.g. ifup ppp1.


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