Friday, August 10, 2007

The modem check

For a successful router setup it is often good to know what kind of modem you have. Many ISPs provide you with a modem through which you can connect to the internet. Some of those modems are not simple modems but are in fact full routers. Cascading routers, however, is not without pitfalls and for the initial setup of the router it is important to understand how the modem operates. You can do a simple check to find out:

  1. Connect your computer directly to the modem.
  2. Verify you have a working internet connection.
  3. Open a command prompt window.
  4. Enter "ipconfig /all"
  5. Open your browser and go to http://whatismyipaddress.com and take a note of your IP address as seen from the internet.

Now compare the IP address shown in the "ipconfig" with the IP address shown in the internet. If both are equal your modem is (most likely) set up as a simple modem. Your computer has a direct connection to the internet through the modem.

If the IP addresses differ your modem (or wherever you have connected your computer to get the internet connection) is a router with address translation, too. Most often, you'll see a IP address like 192.168.*.* in the ipconfig. Your computer is not directly connected to the internet but another device is establishing the connection for you. For a successful router setup you should take a note of the default gatway address which you can see in the "ipconfig /all" output.

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