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By: John Lewis  05/12/2011

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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