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HOWTO_Parallel_Port_Network


This article is part of the HOWTO series.
Installation Kernel & Hardware Networks Portage Software System X Server Gaming Non-x86 Emulators Misc

Contents

Introduction

This HOWTO will guide you in setting up a parallel-port network. You should not need to install anything, but you will need to rebuild your kernel.

You will need a parallel null modem cable, often sold under a "LapLink" name. You should be able to find one at your local computer store or OfficeMax for US$10 to US$20.

Kernel Configuration

Device Drivers  --->
 Networking support  --->
  <*> PLIP (parallel port) support 
 Character devices  --->
  < > Parallel printer support

Note that you cannot have both PLIP and LP support compiled into the kernel. If you MUST use a LP on one of your computers, you'll have to juggle modules.

BIOS Configuration

Make sure that the BIOS for both computers have the parallel port enabled, and in at least bi-directional mode. ECP or EPP would be even better.

Network Configuration

After you reboot your computers, figure out which device was assigned to the parallel ports. Normally they should be plip0. Use whatever they are from here on out.

Next, pick two IP addresses to use. You should try to use ones in the same range as any ethernet adapters in the system. If these are isolated systems, then it matters not what addresses you choose. I'll use 192.168.1.50 on my "router" (which has two ethernet adapters in my configuration) and 192.168.1.55 on my "client" (which has no other network interfaces).

File: Router's /etc/conf.d/net
config_plip0=( "192.168.1.50 pointopoint 192.168.1.55" )
routes_plip0=( "default gw 192.168.1.55" )
File: Client's /etc/conf.d/net
config_plip0=( "192.168.1.55 pointopoint 192.168.1.50" )
routes_plip0=( "default gw 192.168.1.50" )
Code: Execute on both computers
localhost /etc/init.d # ln -s net.lo net.plip0
localhost /etc/init.d # ./net.plip0 start
 * Starting plip0
 *   Bringing up plip0
 *     192.168.1.50                                                       [ ok ]
localhost /etc/init.d # rc-update add net.plip0 default
 * net.plip0 added to runlevel default
* rc-update complete.

That should be all you have to do (note that I haven't tested it with both computers using the new /etc/conf.d/net syntax shown above; you might have to tweak routes_plip0 on the router. I'll update once I get my router updated). You might want to tracepath 192.168.1.5x just to make sure. I have a working setup with my router using the "old" /etc/conf.d/net syntax and the client using the new syntax. If you want one of the computers to route over other interfaces, you might find this to be a good read. I used it to set up my router, and it works great.

I'm having slight difficulty getting other computers on my LAN to be able to connect directly to the PLIP'd computer. I'll investigate and update once I figure something out.

Conclusion

When I hooked my laptop up to my router via my parallel cable, did the ifconfig commands manually, and brought down net.wlan0, I was able to connect to IRC just fine. A little slow, perhaps, but it worked. I didn't try to route data in the other way (incoming connections; such as ident (masquearaded) or a regular port forward (iptables)), but I'd suppose it'd work.

I had some trouble getting it to work at first, but when I checked my kernel config I noticed I forgot to turn parallel printer support off. Once I did that and rebooted, it Just Worked.

If you have any questions, just leave me a message on my talk page.

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Last modified: Fri, 05 Sep 2008 06:33:00 +0000 Hits: 10,692