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Applying Cisco Troubleshooting Tools

Chapter Description

This sample chapter from CCNP Support Exam Certification Guide introduces some powerful troubleshooting tools that are built into the Cisco IOS. As with other tools, it is important that you identify when to use them and what information they reveal. Because some of these tools have an impact on the way routers operate and may impede the routers' utmost performance, it is essential to use them with care. To better understand the output of these commands, and to recognize what router internal operations they affect, this chapter discusses router internal components and operations. As each tool/command is introduced, its usefulness is described and tips are given on how to use it effectively.

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Information Needed by Technical Support

In some troubleshooting cases you have to seek assistance from Cisco Technical Support. When customer support engineers (CSE) at Cisco Systems open a case, they need a set of information from a caller. The following paragraphs list and describe different types of information to furnish to the CSEs.

You must identify your company and your service arrangement. Next, you have to provide a statement of your problem, a brief history of the problem, a list of reported symptoms, an indication of how often the symptoms are observed, and any actions you have taken so far. Network diagram(s) and the output of the show version and show running-config commands are among the most general information you will have to furnish.

If you are dealing with hang or crash scenarios, the output of show stacks and core dump (and exception dump) are usually asked for.

If your case has mostly to do with performance degradation, the following commands' outputs will provide a wealth of related facts, and are therefore necessary:

  • show interfaces
  • show buffers
  • show memory
  • show processes [cpu]

When you face loss of functionality scenarios, for instance, if a protocol or a connection is faulty, the outputs of the following commands are likely to be requested:

  • show protocol
  • show [protocol] protocol
  • show [protocol] route
  • show [protocol] traffic (e.g., show ipx traffic)
  • show [protocol] interfaces
  • show [protocol] access-lists

Regardless of the nature of your problem, the outputs of trace, debug, protocol analyzer captures, and so on may also be asked for.

Also, be aware of the command show tech-support, which displays output equivalent to entering many troubleshooting show commands at once. The show tech-support command output comprises the following sections:

  • show version
  • show running-config (in privileged exec mode)
  • show controllers
  • show stack
  • show interfaces
  • show processes mem
  • show processes cpu
  • show buffers
9. show version Command | Next Section Previous Section