How can I test my network card in case I get DSL?

I want to connect my PC to dsl and I understand that the modem from AT&T used for DSL will plug into the back of my PC into a network connection that looks like a large phone input jack which I do see on the back of my PC. But how do I know the card connected inside still works since I'm not currently using this network jack for anything and never have so far? Is there anyway I can test it?

 

I recommend you go buy a 4-Port Ethernet Router. This will sit between your computer and the modem and connect via the Ethernet port (that network connection on your PC) and one of the ports on the router. If you can log into the router's menu with your browser, it all works. Keep the router in place as this will provide a huge layer of security between you and the badguys. It will also allow you to share your connection with other computers in your home. Any router is a huge improvement over none, but the better ones include SPI (stateful packet inspection) and other features.

Everyone with a broadband connection (cable or DSL) should be behind a router - even if they only have one computer connected.