Troubleshooting Overview

This chapter gives a brief overview of the various areas where you might need troubleshooting and contains the following sections:

General Model of Problem Solving

When troubleshooting a network environment, define the specific symptoms, identify all potential problems that could be causing the symptoms, and then systematically eliminate each potential problem (from most likely to least likely) until the symptoms disappear.

Figure 1-1 illustrates the general problem-solving model. This process is not a rigid outline for troubleshooting an internetwork. It is a foundation on which you can build a problem-solving process for your environment.

Figure 1-1: General Model of Problem Solving

The following steps detail the problem-solving process outlined in Figure 1-1:

Step 1 Analyze the network problem and create a clear problem statement. Define symptoms and potential causes.

Step 2 Gather the facts you need to help isolate possible causes.

Step 3 Consider possible causes based on the facts you gathered.

Step 4 Create an action plan based on those causes. Begin with the most likely problem and devise a plan in which you manipulate only one variable.

Step 5 Implement the action plan, performing each step carefully while testing to see if the symptom disappears.

Step 6 Analyze the results to determine whether the problem is resolved. If so, the process is complete.

Step 7 If the problem has not been resolved, create an action plan based on the next most possible cause in your list. Return to Step 4 and repeat the process until the problem is solved.

Make sure that you undo anything you changed while implementing your action plan. Remember that you want to change only one variable at a time.

Note If you exhaust all the common causes and actions (either those outlined in this publication or others that you have identified in your environment), contact customer service. See "Technical Support," for additional information.

Preparing for Network Failure

It is always easier to recover from a network failure if you are prepared ahead of time. To determine if you are prepared for a network failure, answer the following questions:

1. Do you have an accurate physical and logical map of your internetwork that outlines the physical location of all of the devices on the network and how they are connected, as well as a logical map of network addresses, network numbers, and subnetworks?

2. Do you have a list of all network protocols implemented in your network for each of the protocols implemented and a list of the network numbers, subnetworks, zones, and areas that are associated with them?

3. Do you know which protocols are being routed and the correct, up-to-date configuration information for each protocol?

4. Do you know which protocols are being bridged? Are there any filters configured in any of these bridges, and do you have a copy of these configurations?

5. Do you know all the points of contact to external networks, including any connections to the Internet? For each external network connection, do you know what routing protocol is being used?

6. Has your organization documented normal network behavior and performance so that you can compare current problems with a baseline?

If you can answer yes to these questions, then you should be able to recover from a failure quickly and easily.

Troubleshooting General Problems

This section describes where to find troubleshooting, installation, and configuration information for non-ATM related switch router problems, and includes:

Refer to the following publications for ATM-specific software configuration and command reference information:

Troubleshooting Hardware and Booting Problems

Refer to the following publications for more detailed information about booting problems or specific hardware, including descriptions of specific LEDs, configuration, and additional troubleshooting information:

Refer to Chapter 3, "Troubleshooting Hardware and Booting Problems," in the Internetwork Troubleshooting Guide for general information describing booting problems.

Troubleshooting Ethernet Media Problems

The information referred to in this guide is by no means comprehensive. Instead, it offers solutions to the problems most commonly encountered when using Ethernet media.

Note To troubleshoot ATM physical interface connections, see "Troubleshooting ATM Switch Router Interface Connections," in this guide.

Refer to the Quick Reference Catalyst 8540 CSR and MSR Hardware Information for more detailed information about booting problems or specific hardware, including descriptions of specific LEDs, configuration, and additional troubleshooting information.

Refer to Chapter 4, "Troubleshooting Ethernet," in the Internetwork Troubleshooting Guide for general information describing Ethernet LAN media problems.

Troubleshooting Console, Auxiliary Line, and Modem Problems

Refer to the Processor Installation Guide for more detailed information about specific Ethernet, auxiliary and console port connection information, including descriptions of specific LEDs, configuration, and additional troubleshooting information.

Refer to Chapter 14, "Troubleshooting Dialin Connections," in the Internetwork Troubleshooting Guide for general information describing Ethernet, auxiliary, and console port connection problems.

Troubleshooting TCP/IP

Refer to Chapter 5, "Troubleshooting TCP/IP," in the Internetwork Troubleshooting Guide for general information describing TCP/IP configuration problems.

Note Most TCP/IP configuration commands are entered on the Ethernet interface in the processor card.

Table of Contents

Troubleshooting Overview