My guess is some combination of #2 and/or #3. But since you didn't specify..............
As for cabling. Preferrably you would have a switch. Plug your computer into the switch and using a separate cable, plug the AENT into the same switch. Or plug directly from the PC into the AENT using an Ethernet crossover cable. You could even plug your PC into a switch and then plug the AENT into a separate switch and then run a cable from one switch to the other!
These days a crossover cable is no longer required. I've been connecting my PC to AB hardware with standard patch cable for quite a while now. They auto sense and switch.