Tutorial: WOL - The „Magic Packet “

What is the „Magic Packet “?

In principle, the "Magic Packet" is a standardized data packet containing 4xFF. This data packet is sent directly to the MAC address of a network card. Most modern network interface cards support this basic function natively, but for more network functionality, an operating system is usually mandatory.

Preconditions to be met for setting up a working WOL system restart:

1. Depending on your network configuration, these ports must be open:

   Port 7 – UDP

   Port 9 – UDP

    

2. Operating system and/or the hardware of the respective target system must be configured to handle WOL signals.

   Where is the configuration made on the target system?

   In principle, there are two basic scenarios:

   Configuration work at the operating system
   It is possible to specify whether the operating system allows a "Magic Packet." If allowed, the operating system can be configured to wake up from hibernation mode. The condition is, however, that the operating system is still running at this point, albeit in some kind of deep sleep mode. If the hardware is turned off physically or a complete power loss happens, the hibernation state of the operating system is lost with the power loss.

   Configuration work at the BIOS
   In the BIOS settings, the reception of the "Magic Packet" is controlled directly via hardware settings—the network card itself manages the reception and starts the hardware. However, when the computer is in hibernation mode, the hardware is not responsible for managing a restart—the hibernated operating system must trigger and manage the wake up. The network card will only start the hardware via WOL in the case of a complete power loss during hibernation mode.

Note:
Virtualized systems are a little bit awkward because the network interfaces are normally virtualized. The possibility to pass a WOL signal through a physical network interface in order to start a virtual machine depends on the range of functions provided by the virtualization solution itself. If in doubt, please contact the technical support of the corresponding virtualization solution.

3. Setting up the CS141

   All devices of the CS141 family use colons as separators for the MAC address values.:
   Example:

Create multiple single jobs to power up different devices via WOL. It is not possible to set up one job with different MAC addresses.

Note:
Since the WOL signal is sent to the MAC address of a network card, the IP address and the subnet mask do not matter, as they are used by higher system authorities. These higher network authorities must be up and running first. The port only becomes relevant in the case that the WOL signal has to be routed across networks by a router to other network nodes. Usually, port 7 or port 9 is used for this function, but you have to keep in mind that the ports are managed by the network’s system administrator and can be freely adapted to their preferences and security requirements. In other cases, it is possible that the network hardware may use a hard-coded port number and block all other signals as a form of intrusion prevention. If your WOL signal does not work, check the local IT infrastructure to see if the signal was filtered or blocked by other network devices.