How do I know when my on-board ethernet is dead? (Realtek 8112L LAN controller w/ AI NET2 )

So I have an ASUS P7P55D-E Pro motherboard. It has an on-board Realtek 8112L LAN controller w/ AI NET2. I suspect that my LAN controller is dead but I don't really know for sure. This is what I know thus far:

• Everything was working, I have a triple booted system and ethernet was functional under Linux, Win7, and OSX.
• My ethernet is no longer functional under all three of the operating systems.
• I was experiencing random momentary internet outages before everything finally went dark.
• I don't know much about the AI NET BIOS tool but I believe it just checks for ethernet problems before you boot into an operating system. In any case, it doesn't find a connection upon boot.
• I've checked the connection on a couple of other machines and everything worked fine.

I think I already know the answer to my question, but are there any other possible explanations, or is it dead?

Try reseting the CMOS by removing the battery or jumper method (moving the jumper from pins 1-2 to pins 2-3). Did you lose power recently or brown outs? If your onboard NIC is shot, you could always purchase a PCI NIC card for cheap.

You've pretty much done everything except one easy check: the easiest check with a known working connection is to plug into that exact cable and look at the link lights on the ethernet port; if the card is completely shot they'll probably not be on whatsoever. (This isn't foolproof but if an ethernet port gets shorted out from static this will almost ALWAYS result. It's certainly the easiest first thing to check).