Using PPP and TCP/IP over a null modem connection

This is a very quick crash explanation of setting up a peer to peer IP link over serial. I researched this in order to use RF UART modules. This is what works for me. This is almost entirely ripped from this site (, but I wanted a local copy for myself.


  • Two machines running linux with UART devices as /dev/ttyUSB0, configured at 115.2kbps.
  • pppd installed
  • Of my two RF modules, one has an FTDI UART↔USB chip onboard. The other has UART pins broken out. Connect RTS/CTS.
  • Test the connection between the two units with minicom


On Machine 1:

pppd -detach crtscts noauth lock /dev/ttyUSB0 115200 &

On Machine 2:

pppd -detach crtscts noauth lock /dev/ttyUSB0 115200 &

These commands are nearly identical. The only difference is that the IP addresses (local:remote) are mirrored.

nullserialppp.txt · Last modified: 2020/07/24 17:16 (external edit)
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