Technical Configuration Guide for Wake on LAN with Ethernet Edge Switched
4
November_2010
avaya.com
1. Overview: Wake on LAN
Wake on LAN (WOL) is an Ethernet computer networking standard that allows a shut-down computer to
be booted remotely. WOL is both hardware and software technology to wakeup machines that have been
powered off. This becomes a very valuable tool for administrators that need to perform software
distribution to PC’s. Now, administrators have the ability to perform updates without visiting each machine
and the updates can be performed off-hours so as not to interrupt the end user.
1.1 System Requirements
Wake on LAN support is implemented in the motherboard of the computer. The motherboard must have a
WAKEUP-LINK header onboard and connected to the network card via a special 3-pin cable; however,
systems supporting the PCI 2.2 standard coupled with a PCI 2.2 compliant network adapter typically do
not require a WOL cable as the required standby power is relayed through the PCI bus. Wake on LAN
must also be enabled in the Power Management section of the motherboard's BIOS. It may also be
necessary to configure the computer to reserve power for the network card when the system is shut
down.
1.2 How It Works
The general process of waking a computer up remotely in a LAN can be explained as such:
The target computer is shut down, with power reserved for the network card. The network card listens for
a specific packet, called the Magic Packet. The Magic Packet is broadcasted on the broadcast address
for that particular subnet or the entire LAN. The listening computer receives this packet, checks it for the
correct information, and then boots if the Magic Packet is valid.
1.3 Magic Packet
The Magic Packet is a broadcast frame, transmitted over port 7 or 9. It can be sent over a variety of
connectionless protocols (UDP, IPX) but UDP is most commonly used. The data that is contained in a
Magic Packet is the defined constant as represented in hexadecimal: FF:FF:FF:FF:FF:FF followed by
sixteen repetitions of the target computer's MAC address, possibly followed by a four or six byte
password.
