Seeing whether a machine is connected (while offline)

[Callum]

We have created some in-house software to detect a variety of issues that may happen to any of the workstations. One of the most common issues we have is when a student unplugs the Ethernet cable that is connected to the processor, resulting in the workstation losing its connectivity. Our software does detect whether a machine is offline, but then the issue is how do you differentiate between an offline machine, and a machine that is physically disconnected from the network? We have Wake-on-LAN enabled on all of the machines across the network. My method of detecting physically disconnected machines is by waking up every machine in the ICT rooms (using WoL) and waiting 5-10 minutes, to see which machines still register as being offline. Though this wastes a lot of electricity and is not very ideal.

 

Is there any way of sending a special packet to a workstation, similar to the 'magic packet', to detect whether or not it is physically connected to the network?

[kmount]

Just thinking out loud but I'd imagine your switches may come into play here if the WOL works then hopefully the switch knows where the mac is so you could look at what the switch says for the port in question.

[Duke5A]

Ignore inactivity outside of operating hours? Do these machines have the Intel management engines in them? I think the interfaces will still respond to ping if they're enabled with the machine off.

 

-Edit-

 

Also, are these machines plugged in to managed switches? If so, the easiest way would be to monitor SNMP on the switches for the state of the ports. You could bake this functionality into your home-brewed software, or use an SNMP poller like the 'The Dude.'

Edited February 4, 2015 by Duke5A