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If 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
Chapter 8. Network Interfaces 109
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.

• 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

  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 remote system's IP address. 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.