Wake On LAN with ubuntu causing constant reboots

When powered down to the correct state, name name of which varies from brand to brand of motherboard, not only is the NIC left partially powered on (you'll see the lights blink due to traffic on the network) but the motherboard itself has certain circuitry powered up. That circuitry responds to the signal from the NIC telling it to power back up. Other shutdown modes will prevent one or both those components from being powered up, so the wakeup signal is either not recognised by the NIC or the motherboard doesn't see the signal from the NIC.

As far as "solving" this goes, I have no real ideas. I've also been struggling for years to get it consistently right. Every time I get a new machine I have to start all over. Further, some machines are more cooperative in this regard than others. Some I've had will sometimes wake up but other times won't, even when they've been shut down the same way every time.

My only conclusion is that this is one area the manufacturers need to come to some sort of agreement. They could start with some consistent naming scheme for the various power states.

I better stop there, otherwise people might get the idea this is a pet hate of mine.

I don't know this Dell system, but in all systems I know, you need to turn on WOL in the BIOS. Hibernating Windows would then help with the boot time, but is not required per se.