Followers of the assorted American political scandals of the past 30 or so years will have heard a
congressional investigator ask the question, "What did he know and when did he know it?" The same
question serves an internetworking investigator well. When troubleshooting routing problems, the first
step should almost always be to examine the route table. What does the router know? Does the router
know how to reach the destination in question? Is the information in the route table accurate? Knowing
how to trace a route is essential to successfully troubleshooting an internetwork.