LanHelper -
 Speed up your LAN management


How to turn on remote computers across subnet via Wake-On-LAN

The key that Wake-On-LAN across subnet is IP Broadcast Address. There are several things one should note to make Wake-On-LAN work properly.

(1) Make sure Wake-On-LAN commands (Magic Packet) can reach the targets. Boot the target computer and run a packet sniffer on it and start capturing packet. Then from your computer send Wake-On-LAN commands to the destination by using Wake-On-LAN function. Check the sniffer whether it has captured the Wake-On-LAN data. If it has you would be able to send Wake-On-LAN command to this computer across subnet.

(2) If the target computers cannot be reached, send Wake-On-LAN commands to router that the target subnet is directly attached to. You need configure the router yourself. Please read router's user manual for how to broadcast the Wake-On-LAN data into target subnet so all computers are able to receive Wake-On-LAN data.

(3) The source port LanHelper uses in Wake-On-LAN command is port 9810 and the destination one is port 2304. So if you are using a firewall you need to open the ports for UDP traffic.

(4) You should use unicast address or directed broadcast address. Directed broadcast address is an Internet Protocol address that specifies all nodes on a specified network. For example, send Wake-On-LAN commands to so they can reach all nodes in the 192.168.10.x subnet. For all nodes on the specified network to receive the directed broadcast, each router attached to the network must have enabled directed broadcast.

(5) If the target computers are very difficult to receive Wake-On-LAN data, another choice is use HUB in your network. For example, computer A and B all connect to one same HUB. A is powered down while B is running. When using unicast to send Wake-On-LAN commands to B, computer A and B will all receive the data at the same time. An old, second-hand HUB will help.

(6) How to calculate the subnet-directed broadcast address.
        1. Convert machine address to binary, e.g. = 00001010.11010000.00010100.00000001.
        2. Convert the Subnet Mask to Binary, e.g. = 11111111.11111111.11110000.00000000.
        3. Invert the Binary Subnet Mask, e.g. 11111111.11111111.11110000.00000000 becomes 00000000.00000000.00001111.11111111.
        4. OR the machine address and the inverted subnet mask, e.g. 00001010.11010000.00010100.00000001 OR 00000000.00000000.00001111.11111111 = 00001010.11010000.00011111.11111111 =

From version 1.46 on, the program calculates the address for you. In Wake-On-LAN dialog, click IP Broadcast Address label, then select Internet option, enter IP and subnet mask, click Ok button to calculate.

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