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2007-10-26 10:05:26
Wake on LAN (WoL) support is implemented in the
of the computer. Most modern motherboards with an embedded Ethernet
controller support WoL without the need for an external cable. Older
motherboards must have a WAKEUP-LINK header onboard and connected to
the via a special 3-pin cable; however, systems supporting the PCI 2.2
standard coupled with a PCI 2.2 compliant network adapter typically do
not require a WoL cable as the required standby power is relayed
through the PCI bus.
Wake on LAN must be enabled in the Power Management section of the motherboard's . It may also be necessary to configure the computer to reserve power for the network card when the system is shut down.
In addition, in order to get WoL to work it is sometimes required to enable this feature on the card. This can be done in from the properties of the network card in the device manager, on the "Power Management" tab. Check "Allow this device to bring the computer out of standby" and then "Only allow management stations to bring the computer out of standby" to make sure it does not wake up on every single network activity that occurs. For , there is a concerning this issue.
Please note that, despite it's name, Wake-on-LAN is not restricted to traffic. It works with all network traffic, including traffic.
The general process of waking a computer up remotely over a network connection can be explained thus:
The target computer is shut down, with power reserved for the network card. The network card listens for a specific packet, called the "Magic Packet". The Magic Packet is broadcast on the for that particular (or an entire LAN, though this requires special hardware and/or configuration). The listening computer receives this packet, checks it for the correct information, and then boots if the Magic Packet is valid.
The Magic Packet is a broadcast , transmitted over port 0 (Historically the most common port used), or 7 or 9 (becoming the most common ports used). It can be sent over a variety of connectionless protocols (, ) but UDP is most commonly used. The data that is contained in a Magic Packet is the defined constant as represented in hexadecimal: FF FF FF FF FF FF followed by sixteen repetitions of the target computer's , possibly followed by a four or six password.
