You are out, and the computer you need is sitting at home powered off. Maybe it is the machine with your files, the box you SSH into, the home server that runs your backups, or the gaming PC you want to start before you get back so it is ready. Leaving it running 24/7 wastes power and wears the hardware. The answer is Wake-on-LAN: a way to power on a computer by sending it a small network packet — and you can send that packet from the phone in your pocket.

This guide walks through the entire setup, because Wake-on-LAN has a reputation for being fiddly and almost all of that comes from skipping one of the configuration steps. Get them all right and it just works.

How Wake-on-LAN Works

When a computer is "off," its network card can stay partially powered, listening for one specific thing: a magic packet. A magic packet is a small broadcast containing the target machine's MAC address repeated in a specific pattern. When the network card sees its own MAC in that pattern, it tells the motherboard to power the system on. That is the whole mechanism — no agent software running on the target, no open ports, just the network card watching for its wake signal.

This means three things must be true: the network card must keep listening while the machine is off, the system firmware must allow it, and you must send the packet to the right place on the network.

Step 1: Enable Wake-on-LAN in BIOS/UEFI

Reboot the target computer and enter its firmware setup (usually Del, F2, or F12 during boot). Look under Power Management or Advanced for an option named something like Wake on LAN, Power On by PCI-E, or Resume by LAN. Enable it. While you are there, if there is an ErP or "deep sleep" setting that cuts all power on shutdown, disable it — that setting kills the network card completely and Wake-on-LAN cannot work without it.

Step 2: Enable It in the Operating System

Firmware is half the story; the OS network driver has to allow wake too.

  • Windows: Device Manager → Network adapters → your Ethernet adapter → Properties. Under Power Management, enable "Allow this device to wake the computer." Under Advanced, enable "Wake on Magic Packet." It is also worth disabling Windows Fast Startup, which can leave the card in a state that ignores wake packets.
  • Linux: check with
    text
    ethtool eth0
    and look for
    text
    Wake-on: g
    (g means magic packet). If it shows
    text
    d
    (disabled), enable it with
    text
    ethtool -s eth0 wol g
    , and make it persist across reboots with a systemd service or your distro's network config.

Note that Wake-on-LAN is reliable over wired Ethernet. Over Wi-Fi it depends heavily on the adapter and is often unsupported, so use a cable to the target machine if you can.

Step 3: Get the MAC Address

You need the target's MAC address — the magic packet is addressed to it. The easiest way from your phone: while the target is still on, run the LAN scanner in Network Toolkit. It lists every device on the network with its IP, hostname, and MAC address. Find your computer in the list and copy its MAC. (On the machine itself you can also get it with

text
ipconfig /all
on Windows or
text
ip link
on Linux.)

Step 4: Send the Magic Packet From Your Phone

Open the Wake-on-LAN tool in Network Toolkit and enter the MAC address you copied. On the same local network, that is all you need — send the packet and the machine powers on within a few seconds. Save the device so next time it is one tap.

Waking a Machine From Outside Your Home

On the same Wi-Fi, Wake-on-LAN is simple. From across town it is harder, because a broadcast packet does not cross the internet by default. Two common approaches:

  • VPN into your home network first (many routers offer this), then send the packet as if you were local. This is the cleanest and most secure option.
  • Port-forward a UDP port on your router to the broadcast address. This works but exposes a wake path to the internet, so weigh it carefully and prefer the VPN route when possible.

For most people the realistic pattern is: connect to the home VPN from the phone, send the magic packet, then SSH or remote-desktop into the now-awake machine.

When It Does Not Work

Nearly every Wake-on-LAN failure traces back to one of these:

  • The deep-sleep / ErP power setting in BIOS is still on, cutting power to the card.
  • Windows Fast Startup is leaving the adapter in a non-listening state.
  • You are trying it over Wi-Fi on an adapter that does not support wake.
  • The MAC address is wrong — re-scan the LAN and copy it carefully.
  • You unplugged the machine fully; the card needs standby power, so it must stay connected to mains.

Work through that list and the machine wakes. Once it is configured, powering on your PC, server, or NAS from your phone — from the couch or from another city over VPN — turns an always-on box into an on-demand one, which is better for both your power bill and your hardware.