Technical data

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Troubleshooting Techniques and Tools
This chapter provides information that helps you identify symptoms, isolate
problems, and take steps to resolve your network problem. This chapter also
introduces the tools available to help you monitor and diagnose problems with
your network software, devices, and interfaces.
1.1 Using Symptoms to Identify a Problem
The inability to reach remote hosts and networks is usually caused by one of the
following:
• Physical connection failure
• Underlying transport failure (UDP, TCP, IP)
• Incorrectly configured routing, applications, or services such as BIND
• User error
1.2 Isolating Problems
The first step in problem isolation is to make sure that the TCP/IP Services
product is started. This may seem like an obvious step, but it is frequently
overlooked because error messages may not indicate the product is disabled.
(Instead, the messages returned may be ‘‘invalid host’’ or something similar.) You
may not have stopped the product, but someone else may have. To check whether
the product is running, enter the following command:
$ SHOW DEVICE BG
Device Device Error
Name Status Count
BG0: Mounted 0
BG5: Mounted 0
BG6: Mounted 0
BG7: Mounted 0
BG8: Mounted 0
.
.
.
If the command output shows only the BG0: device, then the product is stopped.
The second step is to reduce the problem to its basic components and to
systematically identify what is and what is not working. Ask the following
questions:
• Does the problem occur all the time or intermittently?
• Does it involve all hosts or is it limited to one host?
• Are there special load or configuration conditions under which you encounter
a specific problem?
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