WakeonLAN

Wake-on-LAN (WOL) is a networking feature that enables a powered-off, suspended, or hibernating computer to be awakened by a network message. It is typically implemented through a network interface card that remains in a low-power listening state to receive the wake signal.

The waking signal is a magic packet: six bytes of 0xFF followed by sixteen repetitions of the target device’s MAC address. The packet is usually delivered as a UDP broadcast to port 7 or 9, though some implementations use other ports. On a local network, a directed broadcast or subnet broadcast is commonly sufficient to reach the NIC.

Requirements for use include: a motherboard and NIC that support WOL, and BIOS/UEFI settings that enable wake events. The NIC driver must be configured to allow the computer to wake, and the power supply and system must support the required low-power state. The network must be able to deliver the packet to the device, which may require router and firewall configuration to permit broadcast frames or to forward wake traffic to a host behind a router.

Use cases and limitations: WOL is commonly used for remote maintenance, automated power management, and scheduled wakeups. Wireless wake support (often referred to as WoWLAN) exists but is less common and depends on hardware and drivers; many laptops do not support WOL over Wi-Fi. Security considerations include the potential for abuse if networks allow broadcast wake packets; protections such as VPNs or tightly controlled forwarding and firewall rules are often recommended.

References to related concepts include standard implementations in Ethernet networking and its role in enterprise IT management.