Ubuntu as a wireless 80211g/n access point/router

Following relatively recent improvements in the Linux wireless stack and driver support it is now possible to setup a Linux machine as an access point, even if you don’t have an Atheros chipset (which was historically the case). Support is patchy but I would say there is a good chance you can do this if you have purchased a laptop with built in wireless in the last 2 years. It is even possible to set one up with a USB wireless adapter (which even Madwifi couldn’t do) if you have an Ralink chipset.

Why would you want to do this? Well, there aren’t that many reasons considering ISP’s routinely hand out wireless routers these days, but I will give you a couple:-

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Wake On LAN over wireless

What is it?

Wake On LAN is a mature technology for switching on computers over a network or remotely.

Why would I want it?

Perhaps you are a techy such as myself and you want to be able to switch customers computers on and work on them remotely (saves having to tell people to leave machines on if you are working after hours).

I also use it to switch on my Ubuntu machine upstairs when I am downstairs (saves me or my better half having to wait for boot or to get a file to or from the machine without physically going up there).

Is it easy to do?

Yes when you know how ;)

Before I go any further I will mention a caveat. Almost all of the WOL howto’s out there mention using a “magic packet” packet to wake the machine. Unfortunately I found out after much head banging and googling “magic packet” doesn’t work over wireless networks, apparently because wireless frames screw the magic packet up so that the wakee doesn’t recognise it any more.

So if you want to use WOL by sending the wake up through a wireless network your options are limited and it depends on the network card you have. At least 2 of the cards I have support a variety of WOL options “pumbg” and the other one only supports “pg”.

  • P stands for PHY activity
  • U stands for Unicast activity
  • M stands for Multicast activity
  • B stands for Broadcast activity
  • G stands for Magic Packet activity

Firstly I tried phy activity that had the unfortunate effect of starting the machine every few seconds. Then I graduated to broadcast which started the machine periodically (my thick wireless router is sending out broadcasts every hour or so). Eventually I settled on unicast here is how to get it working.

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