OS/2 e-Zine! - InJoy a personal LAN in your home with IP Masquerading

InJoy a personal LAN
in your home with IP Masquerading - by Jon Winters

Last December my curiosity was piqued by a good article by Ethan Hall Beyer titled "How to share an Internet connection for little or no cost". This article triggered a chain reaction of ideas in my brain that had me constantly thinking of the benefits of sharing a modem connection.

My situation is a little different from most though, in that my home computer is a web server called Obscura! Obscura stays connected to the Internet all the time on a dedicated ISDN line.

My employer was kind enough to provide me with a killer IBM ThinkPad 760ED. This is a great computer but not being able to dial the laptop in to the Internet without tying up another phone line was a real bummer. So I decided that I needed to set up a LAN in my home office.

Ethan's solution for sharing a modem mentioned above involves running quite a few servers and some client software. While this is a good solution, I always consider many ways to do every project and usually choose the path that involves the least amount of resources. One of my main goals for Obscura is high reliability and I knew that running the SOCKS server would require running a Domain Name Server on Obscura. I have no less than ten programs running 24 hours a day already so I was looking for a simpler solution.

Why I use InJoy

When setting up Obscura it became very important to maintain my connection to the Internet 24 hours a day without interruptions. Most dialers are not up to this task. InJoy, however, is packed with features that help me stay connected and the lean text mode interface is a bonus since it uses less RAM than clunky PM-dialers.

The InJoy dialer also has built in IP-masquerading for sharing its connection with more than one computer. In fact, I found that combined with Warp 4 or Warp Connect, InJoy can get the same results as Ethan's solution, using less system resources. So I decided to set up a personal LAN with InJoy's IP masquerading!

What is IP Masquerading?

Here is some basic information, based on what I pulled from the InJoy WWW site and from the InJoy documentation:

IP Masquerading allows you to share one dial up connection. With it you can use InJoy as an Internet gateway for your LAN even though you have only one IP address and modem.
Install InJoy on one computer and everyone can surf the 'net, get mail, read news, telnet and everything else, from any computer on the LAN, all at the same time!
In addition to sharing the connection InJoy works like a firewall by stopping intruders from ranging around inside your LAN. The outside world cannot gain unsolicited access. My ThinkPad is protected without me blowing a pile of money on routers, firewalls, IP numbers, etc.

I am happy to report that this is very easy to set up and it works great! If you have more than one computer in your house and would like to share a modem connection to the Internet, InJoy and Warp 4 or Warp Connect is all you need.

Well okay, you will need a few other things...

Shopping list for IP Masquerading:

You will need:

One modem
One account with an Internet service provider
One Ethernet Hub
Two computers
Two Ethernet adapters
Two Ethernet cables

note: You can expand the last three ingredients, just keep a 1:1:1 ratio.

Obscura has a 3Com Impact IQ ISDN adapter. My ThinkPad has a 3Com Etherlink III PCMCIA Ethernet card and I decided to keep a good thing going by purchasing a 3Com Etherlink III Ethernet card for Obscura. The hub is the cheapest one available at the local computer "mega-store". It's a MaxTech 5 port unit.

InJoy's IP masquerading will work with any decent Ethernet card and if you want to save some bread you can go with coax cable and you won't even need a Hub. My ThinkPad Ethernet card was 10base-T so I had no choice. (note: the 3Com cards pack a lifetime warranty and work great with OS/2.)

Setting up the TCP/IP network and applying IP Masquerading

If you have the hardware you are ready to get started hooking things up. Just follow these really simple steps:

Download, configure and test InJoy on the computer with the modem.
Install the Ethernet cards in both computers and get them to boot without errors. This went very smoothly with the 3Com cards. Warp came with drivers and the 3Com was auto-detected during OS/2 installation.
On the InJoy computer find and open your TCP/IP Configuration (LAN) notebook.
The only pages that I had to change to enable the LAN interface were the first two. The settings below are an exact copy of what worked for me.
- Page one (GIF, 12.4k), Network. On the network page you will need to check the 'Enable interface' box and choose the 'Manually, using:' radio button. I used IP addresses provided by Bjarne Jensen, the author of InJoy. They are the same ones he uses on his IP masquerading setup. 198.168.1.100 is the IP of the card in Obscura. The netmask on both machines is 255.255.255.0.
- page two (GIF, 9.5k), Routing. Check the 'IP forwarding' checkbox and ADD a new route to the card. Use the same settings in the image linked at the beginning of this sentence.
You do NOT need to run a DNS server, Route daemon or SOCKS server. You only need InJoy.
Look in the System Setup toolbox for the MPTS Network Adapters and Protocol Services icon. Double click to launch and configure.
I needed to configure the NetBios socket access. Of course I chose Obscura as the host name. You should use something else.
Add SET HOSTNAME=YOURNAME to your CONFIG.SYS
Open InJoy and go to the settings for your connection and check the [X] IP MASQUERADING checkbox (GIF, 1.8k).
Now you are done with configuration for the InJoy machine and you should reboot it for changes to take effect.
On the other computer you will need to install and enable the network card for TCP/IP. My employer forces me to use a non-OS/2 operating system. Below is an overview of how the masqueraded computer is set up.
On the client computer you should set up the "gateway IP" to the same IP address that you gave the network card in the InJoy machine (198.168.1.100).
Assign an IP of 198.168.1.200 to the network card in the client computer. Again, this is the IP that Bjarne uses.
Connect the two computers to the Hub with 10base-T or to each other with coax cable.
Go back to the InJoy computer and connect to the Internet.
Boot the masqueraded computer and InJoy your new IP masqueraded Internet connection!

After several weeks of testing I have found InJoy's IP masquerading to be very stable and reliable. There is no noticeable performance hit on Obscura or the masqueraded machine, now dubbed "shadow". Obscura doesn't care if the second computer is connected or not.

I have also been able to FTP files between the two computers because Obscura is running an FTP server. I can even hit my Proxy server at work from "shadow" to access the corporate intranet.

If you have more than one computer in your home and have been thinking of setting up a LAN, InJoy is a great and easy way to connect your personal LAN to the Internet!

InJoy is a product of F/X Communications.

Feel free to e-mail me if you have any questions.

Jon Winters is the owner and operator of Obscura! With the help of a few good friends he is up to all kinds of mischief on the web.

[Our Sponsor: EmTec Innovative Software - OS/2 ISDN, modem and telnet software.]

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