Wake on LAN
Wake-on-LAN (WoL) is a network standard that allows a computer to be turned on or awakened from a low-power state (such as sleep mode or powered-off state) by a network message. This message, also known as a "magic packet", can be sent from within the local network or even from another subnet or even the Internet, if properly configured.
This is accomplished by sending a "magic packet" that arrives as a directed broadcast to all devices within a specific network/subnet. More details follow below:
- Magic Packet: The magic packet is a broadcast frame containing anywhere within its payload 6 bytes of all 255 (FF FF FF FF FF FF in hexadecimal), followed by sixteen repetitions of the target computer's 48-bit MAC address. This special packet provides the signal to wake up the computer.
- NIC Support: For Wake-on-LAN to work, the computer's Network Interface Card (NIC) must support this feature and must be powered even when the system is off. This is typically done via a special power source that keeps the NIC active.
- BIOS/UEFI Support: Additionally, the computer's BIOS or UEFI (the firmware that initializes the hardware when it's powered on) must also support Wake-on-LAN and have it enabled.
Wake-on-LAN is widely used in business environments to manage computers remotely, which helps to save energy (since computers can be left in a low-power state when not in use) and allows for maintenance tasks to be performed outside of normal working hours. It is also used in home environments, for example, to wake up a media server or other device remotely as needed.
Links:
https://forum.networklessons.com/t/ip-directed-broadcast-on-cisco-ios/1327/11?u=lagapides