my westel modem (that I rent from my phone provider) quit working with the internet. My airport extreme seems to be working from the dsl (phone) connection through the westel, then through the ethernet cabled to the airport extreme. Do I need the modem?

This is a little confusing what you are asking here....Are you saying your Internet isn't working? You have to have your DSL modem because that is the only thing that can take the DSL signal and make it work for your computer.

Ok, so are you saying that your Internet is or isn't working? Does it work if you plug your computer directly into your computer and bypass the router (make sure you power cycle the modem when you do this)? If it is working this way, then a new modem isn't going to solve a problem with your Internet not working. If it is going slow (try running a speedtest) then you need to call your phone company to have them take a look at why your Internet is slow. If it runs fine this way and then slows back down when you go back through your router there is something else going on. Try unplugging both the modem and the router, let the modem fully sign back in and connect to the Internet, after it gets signed in, plug your router in, and then after it boots up fully, try running the speedtest again...See if that helps any? Sometimes it's just an IP conflict that happens when the dynamic IP that is assigned by your Internet Service Provider changes and the change doesn't flow smoothly.