Workshop

about your more complex network issues.
You’re also about to learn a lot of the simple-but-powerful concepts that professionals rely on. In addition
to network fundamentals, even the best troubleshooting professional needs:
• Product documentation
• Site documentation
• Additional books and materials
• Observation and common sense
• Black box troubleshooting
• Other support people
To help you get up to speed on network terms and the framework in which networks live, you’ll learn
about “The Telephone Analogy” in Hour 1. After you get through that, you’ll feel pretty comfortable with
this stuff; more importantly, you’ll understand a lot of the main terms and principles of networking. This
will allow you to understand the way a network conversation flows from start to finish, and you’ll start to
understand why your network might be broken. You can skip this if you feel comfortable with networking
terms and principles and want to dive right into the troubleshooting methods.
Troubleshooting a network, particularly a large network, is very much like figuring out a puzzle. If you’ve
got a basic idea about how the network should work, and if you know which piece depends on which
(much like how you always place the edge pieces on a jigsaw puzzle before delving into the middle ones)
and the way information should flow, pointing the finger at the general problem area is usually not a
problem. Once you figure out the general area of the problem, you can then use basic troubleshooting
techniques to figure out which specific piece of the puzzle is causing your grief. After all, you don’t need
to be a Rembrandt expert to do a jigsaw puzzle of a Rembrandt painting, do you?
Let’s take a real-life puzzle that you’d probably be pretty good at troubleshooting. Say that you’re a
teacher; your problem is that you have three boys who tend to cause trouble in your classroom. You will
probably engage in two of the most powerful black-box troubleshooting techniques, “divide and
conquer,” and “the delta method.” You’ll realize that one of the boys is new in town, and the only thing
that has changed recently in your classroom, which up until now has been serene. You separate him from
the group, reasoning that he is almost certainly the cause. By dividing him from the other two boys, and
watching the problem move to another section of the classroom, you rule him in as a cause, and rule out
the other two boys. Easy, right? So, right away, before even reading the rest of this book, you’ve got some
ammunition to use against network problems.
Let’s consider a similar problem to your classroom problem. Since skilled labor is hard to come by, your
retailer has hired some gorillas to come in and install a new PC in your office. They come in, install it,
and everything seems fine. The next day, nobody can send email! One of the gorillas decides that it’s time
to rebuild your email server, but you cleverly realize that the only thing that has changed since yesterday
is the new PC. You insist that the gorillas disconnect it from the network, and voila! The problem
miraculously goes away. Upon inspection, the new PC’s network cable has visible damage to it, which