13.2.5. Dialup Interfaces

13.2.5. Dialup Interfaces

If you are connecting to the Internet via a dialup connection, a configuration file is necessary for the interface.

PPP interface files are named using the following format:

ifcfg-ppp<X>

where <X> is a unique number corresponding to a specific interface.

The PPP interface configuration file is created automatically when wvdial, the Network Administration Tool or Kppp is used to create a dialup account. It is also possible to create and edit this file manually.

The following is a typical ifcfg-ppp0 file: 

DEVICE=ppp0 NAME=test WVDIALSECT=test MODEMPORT=/dev/modem LINESPEED=115200 PAPNAME=test USERCTL=true ONBOOT=no PERSIST=no DEFROUTE=yes PEERDNS=yes DEMAND=no IDLETIMEOUT=600

Serial Line Internet Protocol (SLIP) is another dialup interface, although it is used less frequently. SLIP files have interface configuration file names such as ifcfg-sl0.

Other options that may be used in these files include:

DEFROUTE=<answer>

where <answer> is one of the following:

  • yes — Set this interface as the default route.

  • no — Do not set this interface as the default route.

DEMAND=<answer>

where <answer> is one of the following:

  • yes — This interface allows pppd to initiate a connection when someone attempts to use it.

  • no — A connection must be manually established for this interface.

IDLETIMEOUT=<value>

where <value> is the number of seconds of idle activity before the interface disconnects itself.

INITSTRING=<string>

where <string> is the initialization string passed to the modem device. This option is primarily used in conjunction with SLIP interfaces.

LINESPEED=<value>

where <value> is the baud rate of the device. Possible standard values include 57600, 38400, 19200, and 9600.

MODEMPORT=<device>

where <device> is the name of the serial device that is used to establish the connection for the interface.

MTU=<value>

where <value> is the Maximum Transfer Unit (MTU) setting for the interface. The MTU refers to the largest number of bytes of data a frame can carry, not counting its header information. In some dialup situations, setting this to a value of 576 results in fewer packets dropped and a slight improvement to the throughput for a connection.

NAME=<name>

where <name> is the reference to the title given to a collection of dialup connection configurations.

PAPNAME=<name>

where <name> is the username given during the Password Authentication Protocol (PAP) exchange that occurs to allow connections to a remote system.

PERSIST=<answer>

where <answer> is one of the following:

  • yes — This interface should be kept active at all times, even if deactivated after a modem hang up.

  • no — This interface should not be kept active at all times.

REMIP=<address>

where <address> is the IP address of the remote system. This is usually left unspecified.

WVDIALSECT=<name>

where <name> associates this interface with a dialer configuration in /etc/wvdial.conf. This file contains the phone number to be dialed and other important information for the interface.