Many devices support Wake On Lan (WOL) which is a feature that allows a machine to be woken up if it finds itself in a suspended state - for example, when a PC with a WOL enabled network card (NIC) is powered off, the network card will still be put in a low-powered state. This feature has to be activated, usually from the BIOS and allows a "magic packet" to be sent on the data link layer (layer 2 in OSI) (can be IPX, IP - TCP, or any other but UDP is the most common) and broadcasted within the network. When a network device that supports WOL receives the packet the NIC will signal the PC's power supply or motherboard to wake up the system.

The MagicPacket™ that is sent over the network, IP header aside, contains the following payload:

As an example, given a MAC address 9d:1a:01:20:1c:51 and a password minuet, the data payload sent in hexadecimal will be:

FF FF FF FF FF FF 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51
9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51
9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51
9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51 9d 1a 01 20 1c 51
9d 1a 01 20 1c 51 6d 69 6e 75 65 74

where:

• the first 6 bytes are all 255 or FF FF FF FF FF FF in hexadecimal
• at least 16 repetitions of the 48-bit MAC address.
• an optional 6 byte password for the SecureOn™( possible combinations if the MAC is unknown) feature.

Depending on the manufacturer, one can determine what WOL features the hardware supports.

On Linux, this may be accomplished by installing ethtool and issuing:

ethtool eth0

where eth0 is the interface to be queried. This returns something like the following:

	Supports Wake-on: s
	Wake-on: d

where the letters represent (retrieved from ethtool's man page):

For example, to enable waking on magic packets using ethtool, issue:

ethtool -s eth0 wol g

where eth0 is the interface that will receive the packet.