[SOLVED] Wake On LAN Issues with PC connected to multiple networks

baileyboy125

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Jul 27, 2015
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Hi there,
I've been trying to set up WOL for a server connected to an offline network. The PC I'm sending the packet from has two ethernet ports.
One port is connected to the router which is connected to the internet and the other port is connected to a switch that then connects to offline servers.
Both ports are Intel(r) l211 Gigabit Network Adapters and all servers and PCs involved are running Windows 10.
The problem is that when I try to send a packet to one of the servers nothing happens because the packet is sent to the interface that's connected to the internet, not the offline one.
When I disable the internet connected interface in the control panel the packet is sent to the offline network and the server wakes up instantly (for example 192.168.1.3 in the below example).
How can I specify which interface to send a magic packet to? (I'm using command line based solutions like WolCmd.exe and WakeMeOnLan.exe) Here is a quick diagram of the setup:



Kind Regards,
Bailey
 
It is sometimes hard to say what is going to happen when you put 2 different interfaces in the same subnet. Windows assumes these are actually connected to the same network which can cause major issues. It therefore selects just 1 of the interfaces, how exactly it makes the selection I don't know. You can change it but you will still only have 1 interface active.

This is a invalid design which why it doesn't work.

The easiest solution is to use 2 different subnets, change the second network to say 192.168.2.x

In some ways this should work but it depends on the tool you are using. A wake on lan actually does not have any IP address. It is a broadcast packet with the mac address of the machines to wake. Since it is a broadcast packet it should be sent to all interfaces. Now because you have them in the same subnet windows may be out smarting you and not allowing even broadcasts to be sent. In a way that makes sense since having 2 interfaces in the same subnet you can get broadcast storms.
 
Reactions: baileyboy125
It is sometimes hard to say what is going to happen when you put 2 different interfaces in the same subnet. Windows assumes these are actually connected to the same network which can cause major issues. It therefore selects just 1 of the interfaces, how exactly it makes the selection I don't know. You can change it but you will still only have 1 interface active.

This is a invalid design which why it doesn't work.

The easiest solution is to use 2 different subnets, change the second network to say 192.168.2.x

In some ways this should work but it depends on the tool you are using. A wake on lan actually does not have any IP address. It is a broadcast packet with the mac address of the machines to wake. Since it is a broadcast packet it should be sent to all interfaces. Now because you have them in the same subnet windows may be out smarting you and not allowing even broadcasts to be sent. In a way that makes sense since having 2 interfaces in the same subnet you can get broadcast storms.
 
Reactions: baileyboy125

baileyboy125

Honorable
Jul 27, 2015
87
0
10,640
3
It is sometimes hard to say what is going to happen when you put 2 different interfaces in the same subnet. Windows assumes these are actually connected to the same network which can cause major issues. It therefore selects just 1 of the interfaces, how exactly it makes the selection I don't know. You can change it but you will still only have 1 interface active.

This is a invalid design which why it doesn't work.

The easiest solution is to use 2 different subnets, change the second network to say 192.168.2.x

In some ways this should work but it depends on the tool you are using. A wake on lan actually does not have any IP address. It is a broadcast packet with the mac address of the machines to wake. Since it is a broadcast packet it should be sent to all interfaces. Now because you have them in the same subnet windows may be out smarting you and not allowing even broadcasts to be sent. In a way that makes sense since having 2 interfaces in the same subnet you can get broadcast storms.
Perfect! Thank you. I changed the subnet of the server network from 1 to 2 and now WOL sends on the correct interface. Honestly don't know why I didn't try that before.
It's strange though about your second point. I used Wireshark to check what was being sent and when the internet connected network was active the WOL packet was being sent only to that interface and not the other.

Thanks for your help :)
 

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