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The Problem-Solving Model
15
If you had not gathered such specific information, the list could have
included all of the possible problems with any piece of equipment between
Host A and Host Z. That would have been a long list, and it would take a
lot of time to eliminate all of the possible causes.
Remember that because these are only possible causes, you still have to
create an action plan, implement it, and observe to see whether the changes
made were effective. When the list of possible problems is long, it may
require more iterations to actually solve the problem. In this example, you
have only four possible causes, so this is a much more manageable list.
Although there may be other possible causes that you can think of (that's
great), for this example and in the interest of simplicity, only these four are
listed.
Here's when the fun starts. You now have to check each of these possi-
bilities and fix them if they are the cause of our problem. To do this, move
on to the next step, which is to create an action plan.
Steps 4 and 5: Create and Implement the Action Plan
Creating an action plan is actually very easy. It entails the documentation of
steps that will be taken to remedy the cause of the network problem. Most
of the hard work was done while gathering information about the problem.
The investigation gave you four leads about the source of the problem. Now,
it is simply a matter of checking out each possibility.
The majority of the possibilities point directly at the host machine, so start
there first. The first three causes are configuration issues of the host. Now,
assume that after checking the TCP/IP configuration on the host, everything
is configured properly, and you can eliminate the host machine as the culprit.
You then move on to the last possible cause, which is an access list on
the router. While looking at the configuration on the router, you see that an
access list is applied to the Ethernet 0 interface. After reviewing the syntax of
the access list, you determine that it is the cause of the failure.
Great--you've found the problem. Now what? Once you find the problem,
you must decide what is needed to fix it. In this case, it is an access list pro-
blem, so it will take some special considerations about how to restore func-
tionality. You must be careful because that list may have other entries that
provide security or other network administrative functionality. You can't
just remove it--you could cause new problems as you fix the original one.
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