Configuring SLIP and PPP
The configuration and setup for either Serial Line Internet Protocol (SLIP) or Point-to-Point Protocol (PPP) follows the general TCP/IP configuration you have just completed. Both SLIP and PPP work over a modem, establishing a modem link with a remote system, then invoking either the SLIP or PPP protocols. You can configure SLIP and PPP when you are configuring the general TCP/IP files, or you can wait until you need to set them up for SLIP or PPP access. Not all installations require SLIP or PPP, although many Internet service providers prefer SLIP or PPP access from small systems.
Setting Up the Dummy Interface
A dummy interface is a trick used to give your machine an IP address to work with when it uses only SLIP and PPP interfaces. A dummy interface solves the problem of a standalone machine whose only valid IP address is the loopback driver (127.0.0.1). Although SLIP and PPP can be used for connecting your machine to the outside world, when the interface is not active you have no internal IP address that applications can use.
Creating a dummy interface is simple. If your machine has an IP address already assigned for it in the /etc/hosts file, all you need to do is set up the interface and create a route. The two commands are shown here:
ifconfig dummy machine_name route add machine_name
where machine_name is your local machine's name. This creates a link to your own IP address. If you do not have an IP address for your machine in the /etc/hosts file, you should add one before you create the dummy interface. Add a line with your machine name and its aliases along with the IP address, such as this line:
220.127.116.11 merlin merlin.tpci.com