Wake on LAN: How to Remotely Power Up Your PC

Wake on LAN Explained — Setup, Troubleshooting, and TipsWake on LAN (WoL) is a networking standard that allows you to remotely power on computers over a local network (and sometimes over the internet). It’s useful for remote administration, home labs, and energy-saving workflows where systems are kept off until needed. This guide explains how WoL works, how to set it up on modern hardware and operating systems, common troubleshooting steps, and security and best-practice tips.

How Wake on LAN Works

At its core, Wake on LAN relies on the network interface card (NIC) remaining partially powered when the computer is off. The NIC listens for a specially formed network packet called a “magic packet.” The magic packet contains the target computer’s MAC address repeated multiple times (usually 16 times). When the NIC detects a matching magic packet, it signals the motherboard to power on the system.

Key technical points:

• Magic packet: UDP or Ethernet-frame based packet containing the target MAC address repeated (typically 16 times).
• Layer: Works at Layer 2 (Ethernet) and can also be sent over UDP (often port 7 or 9) for routed networks.
• Power state: Requires the NIC and motherboard to provide standby power; typically works from S3 (sleep) and S5 (soft off) states if supported.

Required Hardware and Firmware Support

To use WoL you need:

• A motherboard and NIC that support Wake on LAN. Many modern desktop motherboards and integrated NICs support it; some laptops limit WoL in battery-powered states.
• BIOS/UEFI option(s) to enable Wake on LAN, sometimes labeled Wake on PCI, Wake on PME, or Wake on LAN.
• NIC drivers in the operating system that support Wake on LAN and proper configuration of power management settings.
• For remote Internet wake-ups, router support for directed broadcast or a VPN to the target LAN.

Preparing the Target Machine

1. Enable WoL in BIOS/UEFI:
   • Enter your firmware settings (commonly Del, F2, or Esc on boot).
   • Look for settings named Wake on LAN, Wake on PCI-E, PCI Devices, Power on by PCI, or similar. Enable them.
2. Configure the operating system:
   • Windows:
     • Open Device Manager → Network adapters → your NIC → Properties.
     • On the Power Management tab, check Allow this device to wake the computer and Only allow a magic packet to wake the computer (if available).
     • On the Advanced tab, enable settings like Wake on Magic Packet, Wake on pattern match, or Shutdown Wake-On-Lan as supported.
   • Linux:
     • Use ethtool to check and set wake-on options. Example: sudo ethtool eth0 and sudo ethtool -s eth0 wol g (where g enables magic-packet wake).
     • Ensure network manager or systemd services don’t fully power down the NIC.
   • macOS:
     • On supported Macs, enable “Wake for network access” in Energy Saver preferences. For some Macs, WoL works only in sleep, not shutdown.
3. Verify NIC remains powered:
   • Look for link/activity LEDs on the NIC when the system is off/sleeping. If present, the NIC likely remains powered.

Sending a Magic Packet

• From another machine on the same LAN:
  • Use tools like wol, wakeonlan (Linux), Depicus Wake On LAN (Windows), or mobile apps to send a magic packet.
  • Command example (Linux): wakeonlan AA:BB:CC:DD:EE:FF
• Across subnets or over the internet:
  • Routers commonly block broadcast packets; you may need to use directed broadcasts (e.g., 192.168.1.255) and enable ip directed-broadcast on the router, which can be a security risk.
  • Safer approach: use a VPN into the LAN and then send a magic packet as if you were local.
  • Alternatively, set up a small always-on relay device (Raspberry Pi) on the LAN that accepts secure wake requests (HTTPS, SSH) and sends the magic packet locally.

Troubleshooting Common Problems

Problem: Computer won’t wake

• Verify BIOS/UEFI WoL settings are enabled.
• Confirm NIC power/wake settings in OS (Device Manager or ethtool).
• Check that the NIC link light is on when the system is off.
• For wireless NICs: most Wi-Fi adapters don’t support WoL from a fully powered off state; WoWLAN (Wake on Wireless LAN) is less widely supported and often limited to sleep states.
• If sending from another subnet, confirm router allows directed broadcasts or use a VPN/relay.
• Ensure the correct MAC address is used and that no MAC changes occur (e.g., virtualization, NIC replacement).
• Check for fast startup or hybrid sleep: on Windows, disable “Fast Startup” (Control Panel → Power Options → Choose what the power buttons do → Change settings that are currently unavailable → uncheck Turn on fast startup). Fast startup can prevent proper WoL behavior because it uses a partial hibernation state.

Problem: Works locally but not remotely

• Router/NAT may drop broadcast packets. Use VPN or a relay device.
• ISP may block certain traffic. Test with UDP port ⁄₇ or directed broadcast.

Problem: Random wakes or false triggers

• Some network traffic patterns or NIC features (pattern match) can wake a machine. Limit wake triggers to magic packet only in OS NIC settings.
• Disable Wake on pattern or Wake on link if unwanted.

Security Considerations

• WoL itself has no authentication — anyone who can send the correct magic packet can attempt to wake the machine.
• Exposing WoL over the internet via directed broadcasts is risky; use VPN or authenticated relay services instead.
• If you run an always-on relay, secure it with SSH keys, TLS, and firewall rules to limit who can request wakes.
• Keep firmware and NIC drivers updated to reduce vulnerabilities around remote wake features.

Practical Examples and Commands

• Linux (check and enable WoL):

  sudo ethtool eth0                # view current settings sudo ethtool -s eth0 wol g       # enable magic packet wake 

• Windows (PowerShell to send magic packet using a small script/module):

  # Example using the WakeOnLan module (install from PSGallery if available) Send-WakeOnLan -MacAddress "AA:BB:CC:DD:EE:FF" 

• Raspberry Pi relay (Python example using wakeonlan module):

  from wakeonlan import send_magic_packet send_magic_packet('AA:BB:CC:DD:EE:FF', ip_address='192.168.1.255') 

Best Practices and Tips

• Prefer VPN or an authenticated relay instead of exposing broadcast wake to the internet.
• Reserve WoL for devices that need occasional remote power-on; keep mission-critical servers on UPS and remote management (IPMI/iLO/DRAC) for more robust control.
• Keep a small always-on device (router, Pi, or NAS) that can accept secure remote commands and send local magic packets.
• Test WoL in your environment before relying on it; verify behavior across reboots, updates, and sleep/shutdown states.
• Document MAC addresses and WoL access methods for each machine.

Alternatives to Wake on LAN

• IPMI/iLO/DRAC: Out-of-band management interfaces for servers that provide remote power control and console access.
• Smart plugs or managed PDUs: For simple power cycling on devices without remote management.
• Cloud-based remote access: For cloud VMs, use provider APIs to control power states.

Wake on LAN is a simple, low-cost tool for remotely powering machines when properly configured. Use BIOS/OS settings, check NIC power behavior, prefer VPN/relay for remote wake, and secure any exposed control points.