Another thing is to 'ping' a known server, such as Zoom. Open the MS-DOS prompt, type ping www.zoomtel.com and press Return. (Note: Make sure the server you attempt to ping responds to ping; many servers do not any longer, and you should not mistake this for a network problem.) If you cannot ping the name of an IP address (it might hang or fail with cannot resolve hostname errors), ping a known, valid IP address. The IP address of your local ISP is a logical start. If you can ping one of your ISP's IP addresses, then you know it is not your DSL line. If it is your DSL line, call your ISP.
The first thing to check is the power, lights and connections. Refer to your manual for lights or status information if necessary. If you're running Windows, a restart is often the best thing to try.