You won't often have to configure WAN connections as a Cisco engineer unless you are out consulting for several companies and setting up new networks. Often though, when your WAN connection is down you will be expected to troubleshoot the problem and pass your findings to your ISP.

If you don't understand how your WAN works and what is causing the problem you will find that your ISP usually blames your network as the culprit. Save yourself hours of hassle and wasted time by learning to configure and troubleshoot WAN connections.