What is Wake-on-LAN (WoL)? A complete guide to remote power-on

Imagine you’re working from a coffee shop, or even just another room in your house, and realize that a critical file sits on your desktop computer, which is currently turned off or in sleep mode. 

In the past, accessing that file meant physically walking to the machine to press the power button. Today, thanks to a networking technology called Wake-on-LAN (WoL), you can power up your computer remotely with a simple digital command.

This guide explores what Wake-on-LAN (WoL) is, how it works, and best practices in detail.

What is Wake-on-LAN? 

Wake-on-LAN (WoL) is an industry-standard network protocol that allows a computer to be turned on or awakened from a low-power state using a network message. Think of it as a virtual power button, it enables a device to transition from sleep, hibernation, or soft-off mode to full operational status when it receives a specific signal from another device on the network.

The main purpose of WoL is remote power control. By keeping the Network Interface Card (NIC) active in a low-power state, a computer can “listen” for a wake-up call. 

This allows users and IT administrators to conserve energy by leaving machines in sleep mode and waking them only when access is needed, rather than keeping servers or workstations running 24/7.

Wake-on-LAN dates back to the mid-1990s, developed collaboratively by AMD and Hewlett-Packard (HP) in 1995. They introduced the concept of a “Magic Packet”, a signal that could wake devices without requiring complex proprietary hardware. 

Shortly afterward, the Advanced Manageability Alliance (AMA), formed by Intel and IBM, adopted the technology, making it a universal standard across modern computing hardware.

How does Wake-on-LAN work?

Wake-on-LAN (WoL) allows a computer to be powered on remotely using network signals, relying on a combination of Magic Packets, MAC addresses, and specific power states. 

The entire process hinges on a special data frame called the Magic Packet. Since the target computer is asleep and its operating system isn’t active, the Network Interface Card (NIC) is designed to scan incoming traffic solely for this specific sequence. 

The Magic Packet starts with 6 bytes of all 255s (FF FF FF FF FF FF in hexadecimal), followed immediately by 16 repetitions of the target computer’s MAC address. When the NIC detects this pattern, it signals the motherboard to start the boot sequence, waking the system from a low-power state.

Because a sleeping computer does not have an active IP address, WoL operates at the Data Link Layer (Layer 2) using MAC addresses. The Magic Packet is typically sent as a broadcast to the entire network segment. 

Every NIC on the network sees the packet, but only the one with the matching MAC address repeated 16 times responds.

Once the NIC recognizes its address, it triggers the motherboard to initiate the boot process. This mechanism ensures precise targeting even when multiple devices share the same network.

For Wake-on-LAN to function, the computer must be in a standby state, not completely powered off. The motherboard supplies trickle power to the NIC so it can listen for Magic Packets. WoL generally works with the ACPI power states S3 (Sleep/Standby), where RAM remains powered; S4 (Hibernate), where the system state is saved to disk; and S5 (Soft Off), where the computer is fully shut down but still plugged in. 

Most modern computers support waking from S3 and S4 reliably, while waking from S5 depends on the motherboard and BIOS capabilities.

Why use Wake-on-LAN? 

Wake-on-LAN (WoL) allows you to remotely wake computers from sleep, hibernation, or soft-off states, combining convenience, energy efficiency, and control.

• For Home users: Access gaming PCs, media servers, or files without leaving devices running 24/7, saving electricity and reducing hardware wear.

• For IT professionals: Remotely manage hundreds of computers for updates, maintenance, and security patches without disrupting work hours.

• Common applications: Enable remote desktop access, wake NAS or servers for backups, and ensure devices are online for automated updates.

WoL is a simple yet powerful tool that saves time, energy, and effort for both personal and business use.

What are the prerequisites for using Wake-on-LAN?

With the correct hardware and software configuration, Wake-on-LAN can reliably power on your devices remotely, making it a convenient tool for both home and enterprise use.

Hardware requirements

The first requirement for Wake-on-LAN is hardware support. Your motherboard must support ATX 2.01 standards or newer to provide the necessary standby power (+5V) to the network card. 

In addition, the NIC itself must be WoL-capable. Fortunately, virtually all integrated Ethernet controllers and PCI network cards produced in the last two decades natively support Wake-on-LAN.

Software requirements

On the software side, two elements are required:

• Sender application: Software on another computer or smartphone capable of generating and broadcasting the Magic Packet.

• Driver configuration: Network drivers on your operating system (Windows, macOS, or Linux) must be set to keep the NIC alert for the wake signal before the computer enters sleep mode.

How to enable Wake-on-LAN?

Enabling Wake-on-LAN (WoL) involves configuring both your computer’s firmware and operating system. Follow these steps to set it up correctly:

Step 1: Activating WoL in the BIOS or UEFI Settings

Before your operating system loads, the hardware must be configured to allow wake-up events:

1. Restart your computer and enter the BIOS/UEFI (usually by pressing Del, F2, or F12).

2. Navigate to the Power Management or Advanced menu.

3. Look for settings labeled “Wake on LAN,” “Resume on LAN,” or “Power on by PME” (Power Management Event).

4. Set the option to Enabled.

5. Save and exit the BIOS/UEFI.

Step 2: Configuring the network adapter in your operating system

Windows:

1. Right-click Start and select Device Manager.

2. Expand Network adapters and right-click your Ethernet controller.

3. Select Properties → Power Management, then check:

   • “Allow this device to wake the computer”

   • “Only allow a magic packet to wake the computer”

4. Go to the Advanced tab, find “Wake on Magic Packet”, and set it to Enabled.

macOS:

1. Open System Settings (or System Preferences).

2. Navigate to Energy Saver (desktop) or Battery (laptop).

3. Click Options if needed and check “Wake for network access”.

Linux:

1. Open a terminal.

2. Check support with:

sudo ethtool eth0

(replace eth0 with your network interface name)

Look for Supports Wake-on:. If it includes g, Magic Packet wake is supported.

Enable it with:

sudo ethtool -s eth0 wol g

Step 3: Finding and recording the target computer's MAC address

You need the unique MAC address of the computer you want to wake:

• Windows: Open Command Prompt and type:

ipconfig /all

Look for Physical Address under your Ethernet adapter.

• macOS/Linux: Open Terminal and type:

ifconfig

Look for ether or HWaddr for your network interface.

How to send a Wake-Up signal and power on a device?

Since a sleeping computer cannot request a wake-up signal itself, the Magic Packet must be sent from another device. This can be done using dedicated software or mobile apps.

Using dedicated WoL software and mobile apps

Popular tools for sending Magic Packets include:

• Windows: WakeMeOnLan (NirSoft), AquilaWOL

• Android: Wake On Lan (by Mike Webb)

• iOS: Mocha WOL

Waking a computer on the same network

• Open your chosen WoL software on a device connected to the same Wi-Fi or Ethernet network as the target machine.

• Enter the MAC address of the computer you want to wake. Optionally, specify the broadcast IP (usually 255.255.255.255).

• Click “Send” or “Wake”. The target machine should power on immediately.

Testing your Wake-on-LAN setup

Before relying on WoL, it’s a good idea to test your configuration:

• Use a packet sniffer or WoL monitor tool on the target machine while it is awake.

• Send a Magic Packet from your phone or another device.

• If the monitor tool detects the incoming packet, your network and firewall are correctly configured to allow WoL traffic.

How Wake-on-WAN differs from standard WoL?

Standard Wake-on-LAN (WoL) works using broadcast packets within a local network. Routers, however, are designed to block broadcast traffic between networks, which prevents WoL from working across the internet.

Wake-on-WAN (WoW) solves this by sending a Magic Packet over the internet to your router’s public IP address. The router then forwards the packet to the specific computer on your local network, allowing you to wake devices remotely from anywhere in the world.

Key challenges: Port Forwarding and Network Configuration

Getting Wake-on-WAN to work is more complex than local WoL and typically requires:

• Port Forwarding: Configure your router to forward UDP traffic on port 7 or 9 to the target machine.

• Static IP or ARP Binding: Since the target PC is powered off, it has no active IP address. Options include:

  • Forward the port to the broadcast address of your network (e.g., 192.168.1.255).

  • Set up a static ARP entry in the router so it remembers which IP belongs to the target MAC address even when the device is offline.

Successfully configuring Wake-on-WAN allows you to wake your computer from anywhere, but it requires careful network setup and router configuration.

What are the best practices for WoL?

To ensure reliability and security, adhere to these practices:

• Configure BIOS/UEFI settings: Always verify deep sleep states (C-states) do not disable power to the PCI/PCI-e slots.

• Set network adapter options (Windows): Ensure "Energy Efficient Ethernet" or "Green Ethernet" is disabled, as these can sometimes cut power to the NIC prematurely.

• Verify hardware compatibility: Use wired Ethernet whenever possible; Wi-Fi wake-up (WoWLAN) is less reliable and requires specific hardware support.

• Ensure stable power connection: The target computer must remain plugged into a power source; removing the power cable usually resets the "listening" state of the NIC.

• Enable WoL only when needed: If you travel with a laptop, disable WoL to prevent battery drain from spurious network activity.

• Restrict WoL traffic on the network: If possible, use VLANs or router settings to ensure Magic Packets can only originate from trusted devices.

What are the common WoL challenges and their solution?

Here are some of the common WoL challenges that user face along with their potential solutions:

Magic packet not reaching the destination

If the computer doesn't wake, the packet is likely being dropped. Ensure you are sending the packet to the Broadcast Address (e.g., x.x.x.255) and not just the last known IP address of the computer, as the router may have flushed its ARP cache.

Incorrect BIOS or network adapter settings

A common culprit in Windows 8, 10, and 11 is "Fast Startup." This hybrid shutdown mode puts the computer into a state that may not support WoL.

• Solution: Disable Fast Startup in Control Panel > Power Options > Choose what the power buttons do.

Firewall or security software blocking the signal

While rare on the sleeping machine (since the OS firewall isn't running), the sending device's firewall might block the outgoing UDP broadcast. Ensure UDP ports 7 and 9 are allowed for outbound traffic on the sender's device.

Conclusion

Wake-on-LAN is a versatile, enduring technology that continues to be highly relevant in today’s era of remote work and smart homes. Whether you’re an IT professional managing a global fleet of workstations or a home user streaming games from your bedroom, WoL seamlessly connects physical hardware with digital access. 

By properly configuring your BIOS, operating system, and network, you can ensure that your computers, data, and processing power are always just a click away, making remote management, file access, and productivity easier than ever.