8.2.5. Dialup Interfaces
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 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, not already discussed, 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 allowspppdto 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 include57600,38400,19200, and9600.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 of576results 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.
