Getting Started Point to Point Protocol (PPP)

PPP is the 'Point to Point Protocol', a protocol used to transport Internet Protocols (IP) across serial links, usually serial ports or machines connected using 'phone lines and modems. For more information about PPP on Linux, have a look at the PPP HOWTO on linux.org.

To use PPP with Linux on the SuperH, you first need to compile the kernel with some additional options. Fire up your chosen configuration editor, and in the 'Network device support' menu enable 'PPP (point-to-point protocol) support' (CONFIG_PPP). This can either be built into the kernel or set up as a loadable kernel module. Similarly you will also need to enable 'PPP support for async serial ports' (CONFIG_PPP_ASYNC). Then rebuild the kernel or modules as normal.

To set up the PPP connection the program pppd is used. As PPP is a symetrical protocol, this can be used for both the client and server end.

To test your configuration, on the host run:

pppd passive /dev/cua0 local 115200 proxyarp local_IP:remote_IP

where /dev/cua0 is the serial port on the host, and the local and remote IP addresses are the IP addresses you want to give the ppp device on the host and the target respectivly.

Then on the target simply use:

pppd /dev/ttySC1 115200 noipdefault

again, adjusting the serial port as required.

There are numerious options you can give pppd, which can either be stored in a configuration file to save having to specify them on the command line. If you want to use ppp with a modem then it is also necessary to set up chat to initialise the modem and dial out. For more information see the relevant man pages, or the PPP HOWTO.