I have a direct ethernet connection between a Windows 10 PC and a Raspberry Pi.
I have the Pi set up as a server that I can hop onto and run a script that will run Etherwake, a command line Wake on lan program, and it works fine when I test it by turning off my computer and letting it sit for a minute, then I run the command and the computer turns on.
But when I let it sit overnight, it doesn't work anymore. Running the script does nothing.
From what I've been reading, a lot of people fix this by messing with some sort of ARP settings on their router, but there isn't a router in this situation- again, its a direct ethernet cable running between the two computers.