[SOLVED] Wake On LAN over multiple vlans

gareththegiant

Honorable
Dec 15, 2015
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Hi All,

Please forgive me if I word this all wrong. I am trying to configure a powershell script or some other resource in order to send magic packets to multiple vlans. From what my (limited) knowledge remembers the magic packages will be stopped by our core switches (Model: S4048-48) does anyone know how to either have the switch re-broadcast the packets or allow the original broadcast. From what I have managed to find out the recommendations have been to have a server or device on each subnet that stays left on that has a task schedule that you then trigger from a "master".

I would like to avoid this if possible as I have roughly 20 odd subnets and would rather just run a WOL from the "master"
 
This is how it is suppose to work I guess.

WoL is a broadcast packet. The reason you have vlans/subnets is to reduce the amount of machines that see the broadcasts. This used to be a huge issue many years ago when the broadcasts hurt the cpu with interrupts more.

Also years ago you could do stuff like send data to the broadcast IP from outside the subnet. So you would send the data to 192.168.1.255. This was disabled by most vendors because it can be used as denial of service attack. You basically smash every machine on the subnet by sending excessive traffic the broadcast IP.
There used to be some way on some cisco switches of changing this but it did not work on all and I forget what they called it. It would have to be a special feature on your switch. Note I am assuming a layer 3 switch here. If it is layer 2 then this function would be on some external router.

This is kinda like DHCP helpers that forward broadcast off the subnet.
 

kanewolf

Titan
Moderator
Hi All,

Please forgive me if I word this all wrong. I am trying to configure a powershell script or some other resource in order to send magic packets to multiple vlans. From what my (limited) knowledge remembers the magic packages will be stopped by our core switches (Model: S4048-48) does anyone know how to either have the switch re-broadcast the packets or allow the original broadcast. From what I have managed to find out the recommendations have been to have a server or device on each subnet that stays left on that has a task schedule that you then trigger from a "master".

I would like to avoid this if possible as I have roughly 20 odd subnets and would rather just run a WOL from the "master"
This would be worth a test. You could ask the network guys to trunk two VLANs to a specific port that has your "master". Then see if that works.
Your network guys may not agree to have all the VLANs on your one port.
My related question, would be how does DHCP work on those 20 VLANs for the PCs? I would expect a Windows dominan for a system that complicated so somehow the domain controllers get to all the VLANs.
 
This is how it is suppose to work I guess.

WoL is a broadcast packet. The reason you have vlans/subnets is to reduce the amount of machines that see the broadcasts. This used to be a huge issue many years ago when the broadcasts hurt the cpu with interrupts more.

Also years ago you could do stuff like send data to the broadcast IP from outside the subnet. So you would send the data to 192.168.1.255. This was disabled by most vendors because it can be used as denial of service attack. You basically smash every machine on the subnet by sending excessive traffic the broadcast IP.
There used to be some way on some cisco switches of changing this but it did not work on all and I forget what they called it. It would have to be a special feature on your switch. Note I am assuming a layer 3 switch here. If it is layer 2 then this function would be on some external router.

This is kinda like DHCP helpers that forward broadcast off the subnet.
 

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