Troubleshooting Magic Packets
Wake-on-LAN can be a frustrating technology to implement. This is because it requires appropriate BIOS, network card and, sometimes, operating system and router support to function reliably. In some cases, hardware may wake from one low power state but not from others. This means that due to hardware issues the computer may be waking up from the "fully off state" (S5) but doesn't wake from sleep or hibernation or vice-versa. Also, it is not always clear what kind of magic packet a NIC expects to see.
In that case, software tools like a packet analyzer can help with Wake-on-LAN troubleshooting as they allow to confirm (while the PC is still on) that the magic packet is indeed seen by a particular computer's NIC. The same magic packet can then be used to find out if the computer powers up from an offline state. This allows networking issues to be isolated from other hardware issues. In some cases they also confirm that the packet was destined for a specific PC or sent to a broadcast address and they can additionally show the packet's internals.
In Windows Vista and higher, one can also determine how the OS was powered up. Running the powercfg /lastwake command in a CMD prompt will list the "Wake Source". The Wake-on-LAN event should also be logged in the System event log.
Read more about this topic: Wake-on-LAN, Principle of Operation
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