Nice to know: What is Wake on LAN?

Here comes the last part of our small series about switching on and off a (Mini) PC. After talking about ACPI and the Power Button we now take a closer look at Wake on LAN.

As the name suggests, "Wake on LAN" (short: WOL) describes a standard to start a PC via the built-in network card. This can be done on the one hand via the local network, on the other hand, WOL offers the opportunity – and here comes the great advantage – to turn on the computer via Internet.


What are the requirements for Wake on LAN?


A prerequisite for Wake on LAN is that both, the motherboard and the network card, support the WOL standard. In addition, ACPI or at least its predecessor APM must be activated in the BIOS and the PC should run a current version of Windows, Linux or Mac OS. With Wake on LAN, a computer can be awakened from the idle states S3 (Standby/STR), S4 (Hibernation/STD) and S5 (Soft-Off). (In our article on ACPI we have explained the different states in more detail.) However, it is important that the network card is permanently supplied with power via a standby branch of the power supply – even if the PC is switched off. In addition, the computer must be connected to the router via a network cable.


How does switching on via Wake on LAN work?

Switching on is done via a so-called "Magic Packet", that is sent to the network card. It contains the hexadecimal value FF six times in succession, followed by the MAC address of the network card, which is repeated sixteen times without pause. This Magic Packet can be sent from another computer on the network. If you are not on site and would like to switch on a PC via Internet, you can use a different PC, a smartphone or even a NAS. Detailed instructions on how to configure a computer for Wake on LAN can be found here.

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