Linux udev is great but if you forget about it, it’s a pain. When you replace a motherboard/network card in a machine, you just expect the primary network device to be eth0 again, but with udev it’s not going to do it.
Ubuntu uses a file at this location to store the udev rules for network cards:
example of what’s in there:
Remove all the rules in the file, reboot and it should sort you out… there’s more complex ways of dealing with it, but I like hitting things with hammers. 🙂