Snow Leopard Internet Sharing WEP


After a long time, I've found something really nice to write about and it's technical and it's about my MBP.

We often go out for field work and for internet we have a CDMA EVDO USB Dongle and we have about 4-5 laptops, so sharing the internet is a issue.

OS X comes with internet sharing which allows any network interface to be shared over Firewire, Bluetooth PAN, ethernet and even Airport(WiFi). When I tried to set it up, I faced issues and the other laptops (Ubuntu machines) were not able to connect. This is contrary to the "Just Works" of Apple.

After some fiddling around, I was able to get to setup a Airport network, using "Internet Sharing" in "Sharing" under "System Preferences", but WITHOUT WEP security. Select the interface to share, in my case the "Huawei Modem" and tick Airport.
If you fail at this step. Try to create a ad-hoc network in OS X, connect to it from another machine. Then disconnect the ad-hoc network and try again from the Internet Sharing. It should now be able to share the internet over Airport and see this icon in the menu bar:

You should now be able to connect from other machines.

This setup worked well for us, because the place were we go for field work is rather remote and nobody around would be hacking into an open network.

But it was still not possible to use this thing in a more "public" place, like during the journey in the train. So I tried many things to make the WEP work and finally was able to isolate the problem.

The main problem is that the WEP authentication implemented by Internet Sharing in OS X ( and I'm only talking about 10.6.8 here, because I've only one Mac), is SHARED KEY. The default for all other operating systems is OPEN KEY, so as soon as you try to connect with another machine, it fails. 

The trick to do it in Ubuntu is:

  1. Try connect to the network, it'll keep trying, but never succeed. 
  2. Then diconnect that. 
  3. Right click on network manager on the top panel, select "Edit Connection...". Goto Wireless, you'll see "Auto ". Select that and click Edit.
  4. Goto to "Wireless Security",  put the key and change the Authentication to "Shared Key".
  5. Save and close
  6. Now connect from network manager in the top panel and connect to OS X shared network.
  7. This should do it, you'll be able to get internet on the other laptops too!
  8. There is no step 8. :)
Now we have a working shared internet. 

You can do a similar thing with Windows also.



P.S.:  One Ubuntu laptop has some problem, staying connected to the wireless network, to which I share the internet over a ethernet patch cable.