Troubleshooting Commands
183
We spoke a little about the effect of process-switching every packet. The
same goes for troubleshooting commands. Because these tools use the Route
Processor, they too can cause high CPU utilization and have adverse effects
on ordinary data that tries to transverse the router.
You will learn how to use several troubleshooting tools. Every one of
these tools is part of the Cisco IOS. There are many show commands that are
supported by the router. In addition to show commands, there is a tool,
called debug, that is used to see specific information regarding packet trans-
fer and exchange.
Part of effectively using these tools is to learn how to use them without
adversely affecting the router or its other processes. You will learn the specifics of
several troubleshooting commands, along with the information needed in order to
use them without causing additional problems on your network.
We start with nonintrusive, Cisco-specific show commands. After discussing
the show commands, we move on to the debug tool. To finalize, we discuss some
non-Cisco-specific troubleshooting tools: ping and traceroute.
show Commands
There are a large number of show commands supported by Cisco IOS. It is
unrealistic to explain each and every one of them in this book. The most
effective and useful show commands are described in the following para-
graphs. To get a rough idea of all of the show commands, execute the show
?
command from the router prompt. Some useful show commands are listed
in Table 4.3.
T A B L E 4 . 3
Frequently Used show Commands
show
Command
Description
access-lists
List access-lists
accounting
Accounting data for active sessions
adjacency
Adjacent nodes
appletalk
AppleTalk information
buffers
Buffer pool statistics
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