Saturday, September 10, 2011

How to turn a Windows laptop into a wireless adapter

Background:

I have a desktop computer with an Ethernet port, a laptop with Ethernet and WiFi, and a house with an Internet connection on WiFi only.

Windows has a nice little utility call "Internet Connection Sharing" (ICS) that should let me plug my desktop into my laptop and use the laptop as a software gateway to connect the Ethernet network to the WiFI network. However, ICS wants to use 192.168.0.1 as the host IP address, which just so happens to be the same address that the house's wireless router is using. This is a problem.

It looks like there are some workarounds, but they either involve registry changes or sound like hacks (i.e. setting static IP addresses before/after initializing ICS to somehow disable the DHCP sever...), so I am using another utility called NAT32, which markets itself as a "Windows software router".

Installation
  1. Download and install the evaluation version from www.nat32.com
  2. Start NAT32. Enter "driver install" into the NAT32 command line to install the NDIS3PKT driver. Reboot.
  3. Setup the Ethernet adapter with a static IP. Turn off all firewalls around it. Connect the desktop to the laptop (normal Ethernet cable is fine; no crossover cables needed for modern Ethernet adapters) and check that they can ping each other.
  4. Start NAT32 again. A configuration window comes up. Select the WiFi interface as the Internet connection. Select the Ethernet as the Private connection. Accept all default configurations
And that's it! I'm posting this post from the desktop! It took like an hour to setup because of the whole firewall thing. I could turn off the Windows Firewall just around the Ethernet connection and keep it up around the WiFi connection, but with McAfee I ended up turning it off entirely because I couldn't figure out how to do it for one connection only.