Wake-on-LAN: setup and troubleshooting

A powered-off machine cannot answer. Wake-on-LAN solves that paradox: it wakes a machine remotely, provided you prepared the ground once. Here are the prerequisites, the configuration and the troubleshooting list.

How it works

Wake-on-LAN relies on a magic packet sent over the local network. The network card of the sleeping machine stays in standby, recognises the packet and powers the machine on. The packet travels on the local network: the target machine must be reachable from another machine on the same network, or through a relay that sits there. It is a packet, not an inbound connection, that wakes the machine: the mechanism’s security lies in its simplicity. That is why wired networks beat Wi-Fi here: the card must stay powered and listening.

Prerequisites, once and for all

Four settings, applied to every machine you want to wake.

• Enable wake in the BIOS or UEFI: a “Wake on LAN”, “Power On by PCIe” or equivalent option.
• Allow wake in the network adapter properties under Windows: power management, “allow this device to wake the computer” and “magic packet wake”.
• Disable Windows Fast Startup, which can block wake after a shutdown.
• Prefer a wired connection: Wi-Fi and Wake-on-LAN do not mix well.

These settings take two minutes per machine, ideally at agent install time. Skip any of them and the wake fails silently: the machine simply stays off.

Configuring Wake-on-LAN in Ubidesk

Once the prerequisites are in place, the Ubidesk side takes two steps.

• Install the agent on the target machine and confirm it reports into device management.
• From the console, trigger the wake on the powered-off machine.

If the machine does not appear in the console, fix the agent before touching the wake settings. From there, the console shows which machines are asleep and which can be woken.

After the wake, the agent reconnects automatically, including after a reboot into Safe Mode. The full sequence, wake, reconnect, takeover, runs without anyone on site.

Troubleshooting Wake-on-LAN

If the machine does not wake, work through this list in order. Each point removes one common cause: Windows updates often re-enable Fast Startup, and firmware updates sometimes reset the BIOS.

• Did a BIOS update reset the settings? Check the wake option first: it is the cheapest fix.
• Did Windows re-enable Fast Startup after an update? This is the most common cause.
• Is the machine hibernating rather than shut down? Some firmware cannot wake from hibernation.
• Did the machine change network card or address? The inventory then points at the wrong target.
• Does a VLAN isolate the machine from the relay? Magic packets do not cross VLANs without dedicated network configuration.
• Was the machine unplugged or knocked out by a power cut? Nothing wakes a machine without power. Some machines have no standby power at all.

Wake-on-LAN and scheduled maintenance

Wake shines overnight: you book a maintenance window, wake machines one by one, apply updates and shut down cleanly. Nobody stands in front of a machine, and users find their devices updated in the morning.

Wake, reconnect, intervene

Wake-on-LAN only powers on. The rest belongs to the agent: automatic reconnection after reboot, including in Safe Mode, then intervention through unattended access. Overnight maintenance becomes possible again, without asking anyone to switch a machine on in the morning. For overnight work, pair wake with a scheduled session: the agent reconnects, the job runs, the machine shuts down.

For IT teams running distributed fleets, it is the missing link between “the machine is off” and “the machine is fixed”. Once set, it asks for nothing more.