Wake on LAN over different subnets

subnetwake-on-lan

I have 3 IP blocks and 3 Cisco Switches. Each switch has its own IP block – 10.45.100.0/24, 10.45.101.0/24 and 10.45.102.0/24

I have got a PC on 10.45.100.0/24 block. I can wake up whole computers (with IP Address, Mac Address, Subnet, Port) in this IP block from C#.

But when I try to wake up another machine from a different IP block it does not work.

This is a Network Problem or code problem? How can I solve it?

Best Answer

This is a fundamental problem: WOL only works inside a subnet, because a WOL magic packet isn't a valid IP packet and therefore is not routable beyound the local LAN.

The wikipedia entry outlines a solution for this problem (subnet directed broadcasts), but I've never seen this in action. Another way around the problem might be to create a WOL proxy agent that forwards WOL packets into other subnets (i.e. as a UDP packet).

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Wake all sleeping machines on subnet

So from everything I have gathered, there is not a way to do this. From what I can tell, the magic packet doesn't differentiate between sleep and powered down.

That doesn't mean remote support is impossible. You just have to attack the problem in another direction. The core tool that you have to overcome this limitation is scheduled tasks. When you create a task, there is an option under "conditions" called "Wake the computer to run this task". This will allow you to run a task when the system is in sleep mode. If the computer is off, it will skip over the command and stay off.

Once you have your tasks setup, just setup an automatic statup time that happens before all of your tasks and you will be able to again manage your systems.

I use "schtasks.exe" to add tasks remotely. It allows you to specify a username and password to use for the tasks and you can overwrite them as needed.

It's a complex system to setup, but can save alot of time and power if you have windows 7 machines across the board.

Firewall – Single m0n0wall – Two LAN Subnets – How To Setup

If the ICMP packet was sent from 192.168.4.37 to 192.168.5.x and the reply is received from 192.168.4.25 I wonder if this could be considered a spoof. In the m0n0wall advanced settings I notice these 2 options:

Spoof Checking blocks packets not sourced from the subnet of the interface the packet was received on
Bypass firewall rules for traffic on the same interface

I don't know the inner workings of m0n0wall. But I wonder if there are system firewall rules added that are not actually shown in the rules web interface that may be blocking the echoreply.

Can you goto /exec.php and post the output of command:

ipfw list

This would probably be of help in debugging.

Best Answer

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Wake all sleeping machines on subnet

Firewall – Single m0n0wall – Two LAN Subnets – How To Setup

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