Subj : Re: Neworking a DOS laptop with PLIP
To   : mary4
From : kirkspragg
Date : Sun Nov 09 2025 19:10:04

 ma>  ki> - if people are interested, I'll be happy to explain how I set it all
 ma>  ki> in more detail.
 ma>  ki> 
 ma> please tell me the details i am really curious how this works

OK here we go!

First thing you need a linux box with a parallel port & you need to disable
IEEE 1284 transfer modes for the kernal parallel port driver.
The only way I found to do this was to recompile the kernel with it disabled. 

If you configure you kernal with `make menuconfig`, you can find that config item under `Device Driver` then `Parallel Port Support`. Then disable `IEEE 1284 Transfer Modes`. 

Recompile your kernel & modules, do what you have to get your distro to use it & reboot!


Next at the dos end, make sure you have the plip packet driver on you machines + MTCP. You will need the plip packet driver loaded and running on your dos machine AND have it connected to your linux machine with your parallel port laplink cable before you setup the link from the linux end, this tripped me up a bit at the start!

Now at the linux end I setup my hosts file to hold the IP address I use for my plip network:
192.168.2.1 linux
192.168.2.2 dos

change this to whatever you need, bearing in mind you have to use a link-local network! Also at the dos end, make sure to setup MTCP to use the correct IP & also to use your `linux` ip as the gateway. Also use a small network netmask like 255.255.255.254.

Cool now to setup your linux box as an internet gateway over plip!

I just created a bash script to do this, if you've setup your hosts file as per above, you should be able to use it with only minor tweaks. Replace `eth0` with whatever you linux's boxes real network adapter is called:

#!/usr/bin/env bash
rmmod lp
modprobe plip
ifconfig plip0 linux pointopoint dos arp up
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i plip0 -o eth0 -j ACCEPT
iptables -A FORWARD -i  eth0  -o plip0 -m state --state RELATED,ESTABLISHED -j ACCEPT

Put ^^ in a .sh file, make it executable with `chmod +x` & run it. That should setup your linux box as a internet gateway! It worked just fine on my debian 13 box.

Just be sure to have plip loaded and runnong on you dos machine & the plip cable connect between the dos machine and linux machine first. 

.... Doublespace?  It's been working great for me so$^!)@$%&

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