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I
n the previous chapters, you learned a great deal about Layer 2
and Layer 3 technologies and protocols. Additionally, you learned very use-
ful information regarding router architecture and very detailed low-level
information for understanding routing technology. With this knowledge,
you will be able to better interpret the information provided by the trouble-
shooting tools and commands.
The time has come to implement all that you have learned, including
applying the methodology from Chapter 1. Once you have the technical
knowledge base, you must apply it by using a troubleshooting template if
you are to efficiently and successfully troubleshoot network problems.
This chapter's format will be different from what you have seen up to
now. Three different types of network problems will be outlined in detail,
and each type will have two scenarios. The intent is for you to take the pro-
vided information and do the troubleshooting. You will see a great deal of
router output and packet decodes from a protocol analyzer. The information
is there for your reference and at times may not have a great deal of expla-
nation. You must look at the output carefully in order to enable yourself to
determine what is happening on the router or network.
For each scenario, you follow the steps outlined in Chapter 1 by listing
observations, gathering facts, and proposing solutions. Because the book
cannot be interactive, the scenarios are intended to accustom you to using
the methodology, but you will not go so far as to actually verify that the pro-
posed solution solved the network problem. Let's begin.
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