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ITGlossary · Communication and monitoring
Wake-on-LAN (WoL)
Network card feature that starts a powered-off computer or server when it receives a special network packet, the magic packet.
Technical level:Intermediate
The magic packet contains the computer's MAC address repeated 16 times. The network card stays in standby with minimal consumption and, when it recognises the packet, tells the motherboard to power on.
With UPS systems, Wake-on-LAN completes the controlled shutdown cycle: after a long outage the servers shut down safely and, when power returns and the battery has recharged sufficiently, the UPS network card or management software sends a magic packet so they start again without a technician visit.
Enable Wake-on-LAN both in the BIOS and in the network card settings, and test it in advance. It normally works only over a wired connection and within the same local network.
Related terms
- NUT (Network UPS Tools)Open-source software that reads the UPS status and shares it over the network, so that several servers and NAS devices can shut down in a coordinated way.
- Shutdown SoftwareSoftware that talks to the UPS and automatically shuts down servers and computers safely before the battery runs out.
- Cold Start FunctionA feature that allows a UPS to be started directly from the battery without utility power.
- Ethernet Port (RJ45)The UPS's Ethernet network port, through which it can be monitored and controlled from any computer on the network via a browser, SNMP or shutdown software.
- Network Management Card (NMC)An interface card enabling remote monitoring and control of UPS systems via network.
- Alarm ContactA relay output on a UPS that changes state on an alarm, such as battery mode, low battery or a fault, to alert an external system.