A guide to Internet Connection Sharing using MS Windows


ICS stands for Internet Connection Sharing. This is a software that in included in all version of Windows starting from MS Window 98SE. ICS allows the MS Windows PC to


 act as a gateway to the Internet. ICS software consist of a router, a NAT (Network 
Address Translator), DNS and a DHCP server. The router will route your internal network to the external network (the Internet). The NAT provides address translation so that you only need 1 IP address for your entire home LAN (Local Area Network). The DNS provides name lookups. The DHCP server assigns IP addresses to the computers in your home LAN.

A typical home LAN consist of several computers. In the diagram below, the home LAN consist of 2 Atari (Atari#1 and Atari #2) and a Wintel PC. The Wintel PC is the ICS PC, and it has 2 network interface - one to connect to the ISP (in green) and the other to connect to your home LAN (in red).

A network request from the Atari computer will flow to the ISP/Internet via the ICS PC. The returning response from Internet flows back to the Atari computer, again via the ICS PC. In this configuration the ICS PC must always be on and connected to the ISP in order for  the Atari computer to access Internet.

Setting up ICS in windows

Install ICS for Win Me

  • ICS in Windows ME is setup from the  Control Panel's "Add and Remove Program" applets. The option is hidden in the "Windows Setup" tab, double clicking on the "Communications" tick box brings out the communications dialog. Tick the Internet Connection Sharing box.
  • Clicking OK all the way, the software will install on the computer, possibly asking you for the CD or reboot at the end.
Windows ICS setup

Configuring ICS

  • During  the installation you will be asked the network adapter that connects to the ISP and the other network adapter that will connect to your home LAN. When asked to make startup floppy disk for your other computers, answer NO as the startup can't be used for the Atari computer.
  • This completes the setup of ICS.
ICS configuration

Accessing ICS settings

  • After installation, the configuration can be adjusted in the Internet Explorer Connections tab.
New button for ICS in IE connection tab
  • ICS in Windows ME is setup from the  Control Panel's "Add and Remove Program" applets. The option is hidden in the "Windows Setup" tab, double clicking on the "Communications" tick box brings out the communications dialog. Tick the Internet Connection Sharing box.
  • Clicking OK all the way, the software will install on the computer, possibly asking you for the CD or reboot at the end.
Windows ICS setup


Install ICS for Win XP
  • Logon as Admin on your Win XP computer
  • Go to the control panel and call up the Network applet
  • Select your adapter with the Internet Connection, right-click properties for the properties page.
  • Notice the other network adapter has no or limited access.
  • At the properties page, select the Advanced Tab
  • This brings up the Internet Connection Sharing options
  • Just tick the "Allow other network users.... " to share this connection.
  • You may fine tune the Settings or leave it as default.
  • Click OK to complete the setup
 
  • When Windows complete configurating, you will be back at the Network Applet.
  • Noticed that your Internet Connected adapter is now shared.
  • The other network adapter on your internal home network is also connected.
 

IP address assignment on the Atari

The ISP will assign a IP address to your Wintel PC for the interface that is connect to the Internet. This IP address is different from the IP address that you gives you Atari computer.

In the ICS configuration, the home LAN is defaulted to the private address IP subnet of 192.168.0.xxx where xxx is from 1 to 254. Being a private IP address range, no computer on the Internet will have this addresses. The ICS PC home LAN interface (that's the network card connected to the home LAN) will obtain an IP address of 192.168.0.1. This is by default and the recommendation is not to change this. The rest of the computers in the home LAN can take on any IP address number from 192.168.0.2 to 192.168.0.254.

This setup is for STING TCP/IP stack. Using Mintnet or MagiXnet TCP/IP stack will require different setup. However, the values of configurations (IP address, DNS and gateway) are the same for all TCP/IP stacks.  Install STING on the Atari computer and

Atari IP Setup

The STING IP address is setup using the STING PORT CPX. Set the IP address to any valid address within the default subnet range.

The example sets the address to 192.168.0.228 for one Atari computers. The Ethernet0 is the Ethernet device as reported during boot up. Make sure that this device is selected when configuring the IP address. This device name is used in the ROUTE file later.

   

DNS Setup

The STING Resolver (DNS) must point to the DNS server of the ICS PC or the DNS of your ISP.

It is easier to point to the ICS PC as that address is fixed and controlled by you. If you set the DNS of your ISP, be sure that the ISP does not change the DNS address. This information can be obtained from the ISP webpage or by doing a IPCONFIG in the ICS PC in the DOS prompt.

ROUTE.TAB file setup - the default gateway

One last thing to do is to set the route table file. The route will be to direct all traffic not destine for the home LAN out to the router. In this case the router will be the default gateway (ICS PC). The below route line is added to the last line of the ROUTE.TAB file

           0.0.0.0        0.0.0.0     Ethernet0       192.168.0.1

Testing the setup

Reboot all the computers to make sure that everything starts up correctly. On the Atari computer perform these tests

  1. Ping your local host (127.0.0.1) and IP address (192.168.0.228 - in this example).
  2. Ping the default gateway - 192.168.0.1
  3. Ping the ISP assigned IP address for you ICS computer (this is your external IP address).
  4. Ping the ISP DNS server.

If any of them fail, check the configuration of the ICS PC, making sure that the network interface is correctly defined and that the ICS software is enabled.

When all is well and you can ping all the hosts, fire up CAB. Reconfigure it to use a proxy server if required by your ISP. This proxy server information is easily obtainable from their website or you can check the ICS PC Internet Explorer configuration.

 

Voila... is that Probe House Software web page on the Falcon?


update: 31 Jul 2012

created: 5 April 2003