updated and now double NAT?

I have one, and only one, router, the apple basestation extreme. I just updated the firmware (an alert showed in airport utility app) and now I have the double NAT message. It tells me to go into bridge mode, so I did, as I could no longer use the internet. When I did I now see other drives that are NOT on my network.

I live at the university where I teach- the ethernet cable that I plug into the basestation comes from the wall jack (not sure if that is pertinent or necessary--just trying to show I only have one router).