How-to guides · 6 min read
How to wake a powered-off computer for remote access
Written for: IT teams supporting out-of-hours patching, home workers reaching office desktops, and anyone tired of asking users to leave machines on.
In short
Remote access needs the target machine to be running. Wake-on-LAN solves half of that problem by sending a specially formed network packet that powers a sleeping or soft-off machine back on. It works well on wired, same-subnet devices with the right firmware settings, and it is unreliable or impossible in several common situations worth knowing about in advance.
Key takeaways
- Wake-on-LAN has to be enabled in two places: the machine firmware and the operating system's network adapter settings.
- It is a broadcast, so it does not cross subnets or reach across the internet without a relay on the same network.
- Wi-Fi wake is unreliable on most hardware. Treat wired as the supported path.
- Fast startup on Windows can prevent wake from a soft-off state, and is a frequent cause of unexplained failure.
- Where wake is not viable, scheduled power-on in firmware or a simple always-on policy for a defined set of machines is often the pragmatic answer.
How wake-on-LAN works
The network adapter stays partially powered when the machine is asleep or soft-off, listening for a specific broadcast frame addressed to its hardware address. Receiving it triggers a power-on. Nothing else on the machine is running, which is precisely why the feature has to be implemented in the adapter and the firmware rather than in software.
That also explains the limitations. Because the packet is a broadcast on the local network segment, it does not route across subnets or the internet on its own, and anything that changes the machine's power state handling can break it.
Getting it enabled
There are two switches, and both must be on. In firmware, the setting is typically called wake-on-LAN, power on by PCIe, or resume by LAN, depending on the manufacturer. In the operating system, the network adapter's power management properties must allow the device to wake the computer, and specifically to do so only on a magic packet, so ordinary network chatter does not wake it constantly.
On Windows, also check fast startup. It puts the machine into a hybrid state that many adapters will not wake from, and disabling it resolves a large share of cases where everything else looks correctly configured.
- Firmware: enable wake-on-LAN, resume by LAN or power on by PCIe
- Adapter properties: allow this device to wake the computer, magic packet only
- Windows: disable fast startup if wake from soft-off fails
- Record the machine's MAC address, because that is what the wake packet targets
Crossing networks
Sending a wake packet from outside the local segment needs help. The standard approach is to have a device that is already awake on the same subnet forward the packet on your behalf: another always-on machine, a management appliance, or a router that supports directed broadcast forwarding.
Many organisations use a small always-on machine per site for exactly this purpose. It is unglamorous and it works, and it also gives you a reachable device to diagnose from when a site appears to be entirely offline.
When to stop trying
Wi-Fi wake support depends on the adapter, the driver and the access point all cooperating, and frequently one of them will not. Laptops in a bag, machines on hotel networks, and anything behind a captive portal are not going to answer regardless of configuration.
In those cases, decide the policy instead of fighting the technology. A defined set of machines that stay powered on, or a firmware-scheduled power-on before the patch window, is more reliable than wake-on-LAN across an estate that was never wired for it.
Enabling wake-on-LAN end to end
1. Confirm the machine is wired
Start with Ethernet. If wireless wake is a requirement, verify it on one device before assuming it works across the estate.
2. Enable it in firmware
Look for wake-on-LAN, resume by LAN or power on by PCIe. The wording varies by manufacturer, the effect is the same.
3. Configure the network adapter
Allow the device to wake the computer, and restrict waking to magic packets so stray traffic does not power it on repeatedly.
4. Disable fast startup on Windows
The hybrid shutdown state prevents wake on a lot of hardware. This is the most common single fix.
5. Record the MAC address
Store it against the device in your inventory. The wake packet is addressed to the hardware address, not the IP.
6. Provide a relay for remote sites
Nominate an always-on device on each subnet to forward wake packets, since broadcasts do not route by themselves.
7. Test from a cold state
Shut the machine down fully, wake it, and connect. Testing only from sleep hides the fast-startup problem entirely.
Common mistakes
- Enabling wake in firmware but not in the operating system's adapter settings, so it never works and nobody can see why.
- Leaving Windows fast startup on and concluding the hardware does not support wake.
- Expecting a broadcast packet to cross subnets or reach a site over the internet unaided.
- Relying on Wi-Fi wake across a mixed laptop estate.
- Waking machines for a patch window with no matching plan to shut them down afterwards.
Frequently asked questions
- Can I remotely access a computer that is turned off?
- Not directly, because nothing is running to answer. Wake-on-LAN can power the machine on first, provided it is enabled in firmware and the network adapter, and the wake packet can reach the machine's network segment.
- Does wake-on-LAN work over the internet?
- Not on its own. The wake frame is a local broadcast. You need something already awake on the same subnet to forward it, such as an always-on machine, a management appliance or a router that supports directed broadcasts.
- Why is wake-on-LAN not working?
- In rough order of likelihood: fast startup is enabled on Windows, the adapter's power management setting is off, firmware support is disabled, the packet is not reaching the right subnet, or the machine is on Wi-Fi where support is unreliable.
- Is there an alternative to wake-on-LAN?
- Firmware-scheduled power-on before a known maintenance window, or a policy that a defined set of machines stays powered on. Both are less elegant and considerably more predictable.
How this works in 247connect
Once a machine is awake, 247connect connects to it as a managed device in around eight seconds, so pairing a reliable wake method with fast connection times is what makes out-of-hours maintenance practical.
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