Put simply, Wake on LAN is a feature found in most network cards which allows you to remotely turn a machine on. It works by detecting for a certain "magic" packet. When received by the card, it will boot the machine. Wake on LAN is sometimes abbreviated WOL.

What you need

  • A suitably equipped motherboard.

    Most modern motherboards now come with a Wake on LAN connector. This is used by the network card to signal the machine to turn on.

  • A suitably equipped NIC.

    Again, most modern network cards now come with a Wake on LAN connector on them. They need to be able to detect the magic Wake on LAN packet.

  • A Wake on LAN cable

    This connects the NIC to the motherboard.

  • No special OS support

    Wake on LAN is done entirely in hardware. You do not need to install any special software on your machine to enable Wake on LAN on it. (You need software on another machine to send the data needed to boot it)

How to set up Wake on LAN

  1. Obtain above list of needed hardware.
  2. Open your machine up.
  3. Connect the NIC to the motherboard with the cable. I had to remove one of my other expansion cards while doing this on my machine as the Wake on LAN connector was underneath it. The connector is three pin and identical at both ends. If in doubt, look at the manual for your motherboard.
  4. Switch on your machine and go into the BIOS setup.
  5. Check that Wake on LAN is enabled in your BIOS, otherwise your machine will not boot.
Once you have done this, Wake on LAN should work.


To boot a machine using Wake on LAN, you must know the MAC address of the network card. You then need a tool to send the magic wake up packet. I use etherwake by Donald Becker. You can find it here:
This is for Linux; obviously, wake up tools exist for other operating systems as well.

First you must obtain the MAC address. In Linux, you can find this through the "ifconfig" program. Under Windows you can use "ipconfig".

$ ifconfig
eth0 Link encap:Ethernet HWaddr BA:DD:AD:BE:EF:40
inet addr: Bcast: Mask:
The MAC address is displayed in the "HWaddr" field. Here it is "BA:DD:AD:BE:EF:40".

To boot a machine with this MAC address, then:

$ etherwake BA:DD:AD:BE:EF:40

How it works

The network card listens to the network for its MAC address repeated 16 times. If it finds such a packet, the card enables the output to the Wake on LAN connector, telling the motherboard to boot the machine.

I have only tested this by booting from a machine on the local network, but this presumably means you can boot machines on remote networks by sending packets to the broadcast address for that network.

Further information

Some cards support "passwords", stopping malicious people booting machines when you dont want them to. This isnt very common, however.

The Wake on LAN connector can be used to boot the machine for other reasons; some modems support Wake on Ring, for example.

The Wake on LAN mini-HOWTO is useful:


Wake on LAN is a standard for a motherboard to, when switched off, power an external device, which can then instruct the motherboard to switch on. While named 'wake on LAN', absolutely any device may be used, so long as it has a sufficiently low power requirement.

A WOL capable motherboard provides a WOL connector1 :

1 - +5v Standby
2 - Ground
3 - PME (Power Management Enable)
The +5v pin may be used to power the device - if the device has sufficiently low power requirements, it can be powered by the WOL header alone. Pulling pin 3 to +5v causes the motherboard to wake up (if it is not already awake). For WOL to work, the power supply must provide sufficient standby power to supply both the motherboard and any connected devices: while an ATX motherboard may only require .5w, a modern ATX with a WOL device connected may draw up to 10w. If the power supply is not designed for this, the motherboard may not receive enough power to turn on, and may even damage the power supply by drawing too much current.

In modern motherboards (PCI 2.2 or later), these signals are replicated on the PCI and Cardbus busses. A compatible NIC plugged into such a PCI or Cardbus slot does not need a cable for WOL functionality. PCI 2.2 provides 3.3v rather than 5v standby power, thus older 'cable style' WOL cards will not work without modification. Most PCI 2.2 motherboards therefore provide a WOL header for backwards compatibility.

While the standard is called 'Wake On LAN', the device plugged into the WOL header need not be a NIC, or even a card. Internal modems with 'Wake on Ring' use the WOL header to wake the motherboard. The WOL header is ideal for connecting homebrew devices to wake the computer up by other means - infrared remote controls, or powerline home automation devices, for example.

I cite:
"PC Infrared Remote Receiver", Silcon Chip Magazine :
"PCI Bus Power Management Interface Specification", Intel Corp. :

1 - Conversely, any motherboard with a WOL header is WOL capable. It is a common misconception that the motherboard must provide PCI standby power: in fact, the NIC is powered by the WOL header. In some cases, the NIC need not even be plugged into a PCI slot.

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