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WOL Configuration Page

The WOL Configuration preference page Pic 1 is used to configure the Wake-On-LAN (WOL) functionality built into Remote Shutdown. To access this preference page press the Preferences button from the Application Menu and select the WOL Configuration link in the navigation bar on the left of the opened dialog.

Configuring the Wake On LAN functionality

Pic 1. Configuring the Wake On LAN functionality

You can choose the UDP port to be used for sending Wake-on-LAN package in the Remote UDP port field. UDP traffic through this port should be forwarded on the routers that connect the Machine Remote Shutdown is running on with the Machines you want to wake up.

The other thing to specify is one or more of the transmission methods to be used for sending the packet. You can choose from the following methods:

Broadcast – should be used to wake up the Machines from the same subnet the PC with Remote Shutdown running is located in using a broadcast.
Unicast – should be used to wake up the Machines using the Machines' IP address. This is a more secure solution but Wake On LAN will fail to find target computers that have changed their subnet address since the last hardware inventory schedule.
Directed broadcast – should be used to wake up Machines from different subnet, according to the subnet mask specified, using a directed broadcast.
Internet – should be used to wake up Machines over the Internet using the IP address of the Machine, modem or router and the subnet mask.

Power Peaks Settings allows you to set a timeout to wait for before waking up next range of Machines along with the number of Machines that can be waken up at one moment though reduce the load on the electricity network while waking up a large number of Machines.

Transmission methods used for sending WOL packets

Let us take a closer look on each method of forming a destination address for the magic packet to be sent.

The Broadcast method is using the 255.255.255.255 address as a destination address. This is a broadcast address that stands for this network – it means that the magic packet is sent to all Machines from the subnet Remote Shutdown host machine is located in. For example, let us suppose that Remote Shutdown is running on the MERCURIUS machine that has the 192.168.1.10 address and is a part of subnet with the 255.255.255.0 mask. In such a case all the Machines from the 192.168.1.0 network will receive the packet.

The Unicast method is using an IP address of the remote Machine to send the magic packet to. In such a case the magic packet will be delivered only if the ARP cache still contains the entry that stands for the address specified. This method will also fail if the remote Machine host could not be resolved.

For more information about the unicast transmission see the Transmission methods overview section.

The Directed Broadcast is a datagram which is sent to the broadcast address of a subnet to which the sending machine is not directly attached. The directed broadcast is routed through the network as a unicast packet until it arrives at the target subnet, where it is converted into a link-layer broadcast. Because of the nature of the IP addressing architecture, only the last router in the chain, the one that is connected directly to the target subnet, can conclusively identify a directed broadcast. Directed broadcasts are occasionally used for legitimate purposes, but such use is not common outside the financial services industry. The broadcast address is calculated using the IP address of the remote Machine and the specified subnet mask. Let us suppose we are running Remote Shutdown on the MERCURIUS machine that has the 192.168.1.10 address in and is a part of subnet with the 255.255.255.0 mask. This case is quite simple – if we are going to wake up the TYRONE machine that has the 192.168.5.1 address the packet will be sent to 192.168.5.255 address – note that it will be delivered till the 192.168.5.0 network router as a unicast. The more complex case if, for example, the 255.255.255.192 mask is used, dividing the C-class network to four subnets. If we are going to wake up the TYRONE machine that has the 192.168.5.1 address the packet will be sent to the 192.168.5.63 address, and for LAB-PDC with the 192.168.5.130 address – to 192.168.5.191. So in any case the packet should be received by the destination subnet.

Warning

Please notice that routers default configuration does not allow broadcasts between different subnets to protect from network attacks, but you can allow broadcasts only from the Remote Shutdown hosting Machine via the port defined in the preferences. This method will also fail if the remote Machine host could not be resolved.

For more information about the broadcast transmission see the Transmission methods overview section.

The Internet method should be used to wake up Machines over the Internet or from a specific subnet. To wake up Machines over the Internet you should specify the IP address or host name of the Machine, modem or router visible from the Internet and leave subnet mask the 255.255.255.255. In such a case the packet will be sent to the address specified using the Unicast transmission – the router should be configured to forward the packets received to a specific Machine or the whole subnet for the Wake-on-LAN to succeed. The other case of using this method is waking up the Machines from a different subnet that cannot be resolved. To reach the goal the IP address of any Machine from that subnet should be provided along with the subnet mask used for the interested subnet. The packets will be sent to that subnet using the Directed Broadcast transmission.