Network Problem Troubleshooting Flowchart
As a network technician, you'll be called on to troubleshoot problems with
networking hardware, operating systems, applications that use the network, and
other network resources. The flowchart in Figure 1-24 illustrates the method
used by most expert networking troubleshooters to solve networking problems.
Step 1: Identify the problem and its symptoms - As you gather information
about the problem, begin by identifying the symptoms, questioning the user, finding
out what has recently changed, and determining the scope of the problem. If possible,
duplicate the problem. For multiple problems, approach each problem individually.
Solve it before moving on to the next.
Step 2: Establish a theory of possible cause - As you observe the extent
of the problem, make your best guess as to the source of the problem. Troubleshooters
generally follow the bottom-to-top OSI model by first suspecting and eliminating
hardware (for example, a loose cable or failed NIC), before moving on to software
as the cause of a problem. As you question the obvious and check simple things
first, such as a loose network cable, you might solve the problem right on the spot.
Some situations are obviously software related, such as when a user cannot log
on to the network and gets an invalid password message. Here it makes more sense
to follow the top-to-bottom OSI model, beginning at the Application layer, and
suspect the user has forgotten his or her password.
As you work, use a divide-and-conquer approach by eliminating parts of the
whole until you zero in on the source of the problem.
Step 3: Test your theory to determine the cause - For more complicated or
expensive solutions, test your theory to assure yourself that it will indeed solve
the problem before you implement the solution. If your test proves your theory is
wrong, move on to another guess or escalate the problem to the next tier of support
in your organization.
As with any computer-related troubleshooting, be sure you choose the least
invasive and least expensive solution first before moving on to more drastic or
expensive changes to a computer or the network.
Step 4: Establish a plan for resolving the problem - Changes to a network
have the potential for disrupting a lot of people's work. Before you implement a fix,
consider the scope of your change, especially how it will affect users, their
applications, and their data. Unless the problem poses an emergency, make your
changes when the least number of users are on the network.