© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicCourse v6 Chapter #

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Chapter 2:Troubleshooting Processes for Complex Enterprise Networks

CCNP TSHOOT: Maintaining and Troubleshooting IP Networks

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Chapter 2 Objectives

Identify troubleshooting principles and evaluate troubleshooting methodologies.

Plan and implement troubleshooting procedures as part of a structured troubleshooting methodology.

Plan and implement troubleshooting and network maintenance procedures to effectively support each other.

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Troubleshooting Methodologies

Flow chart of a structured troubleshooting approach

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Troubleshooting Methodologies

Shoot from the hip vs. structured troubleshooting method

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Troubleshooting Approaches

Top-down Bottom-up Divide and conquer Follow-the-path Spot the differences Move the problem

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Troubleshooting Approaches - Spot the Differences Example

Branch1 is in good working order

Branch2 has connectivity problems Branch2# show ip route <output omitted> 10.0.0.0/24 is subnetted, 1 subnetsC 10.132.126.0 is directly connected, FastEthernet4C 192.168.37.0/24 is directly connected, BVI1

Branch1# show ip route <output omitted> 10.0.0.0/24 is subnetted, 1 subnetsC 10.132.125.0 is directly connected, FastEthernet4C 192.168.36.0/24 is directly connected, BVI1S* 0.0.0.0/0 [254/0] via 10.132.125.1

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Troubleshooting Approaches - Move the Problem ExampleLaptop B is having network problems. Cable or port swapping can help isolate the problem.

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Implementing Troubleshooting Procedures

Defining the problem Gathering information Analyzing the information Eliminating possible problem causes Formulating a hypothesis about the likely cause of the

problem Testing that hypothesis Solving the problem

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The Troubleshooting Process – Verify and Define the Problem

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The Troubleshooting Process – Gather Information

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The Troubleshooting Process – Analyze

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The Troubleshooting Process – Eliminate

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The Troubleshooting Process – Propose Hypothesis

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The Troubleshooting Process – Test Hypothesis

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The Troubleshooting Process – Solve Problem

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The Troubleshooting and Network Maintenance

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The Troubleshooting and Network Maintenance – Cont. Accurate documentation is critical to effective

troubleshooting. A network baseline is essential and can include:

• Interface load for critical network links (IOS)

• CPU load and memory usage of routers and switches (SNMP)

• Accounting of network traffic (NBAR, NetFlow)

• Measurement of network performance characteristics (IP SLA)

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Communication and Change Control

Communication plays a role in all phases of structured troubleshooting.

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Communication and Change Control – Cont.

Change control is a fundamental process in network maintenance. Controls when changes are made, authorization required and what

actions are taken. Can reduce unplanned outages and increase network uptime. The change control process:

• Implement the change

• Verify that it achieved the desired results

• Roll back if necessary

• Back up the changed configurations or software

• Document/communicate your changes

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Disaster Recovery Tools

Successful disaster recovery is dependent on the existence of the following: • Up to date configuration backups

• Up to date software backups

• Up to date hardware inventories and documentation

• Configuration and software provisioning tools

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Chapter 2 Summary

The fundamental elements of a troubleshooting process:• Gathering of information and symptoms• Analyzing information• Eliminating possible causes • Formulating a hypothesis• Testing the hypothesis

Some commonly used troubleshooting approaches are:• Top-down• Bottom-up• Divide-and-conquer• Follow-the-path • Spot the differences• Move the problem

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Chapter 2 Summary – Cont.

Useful data to gather and create a network baseline are:• Basic performance statistics using show commands

• Accounting of network traffic using RMON, NBAR, or NetFlow statistics

• Measurements of network performance characteristics using the IP SLA feature in IOS

Communication is an essential part of the troubleshooting process and happens in all stages of troubleshooting:• Report the problem

• Gather information

• Analyze and eliminate possible causes

• Propose and test a hypothesis

• Solve the problem

Change control is one of the most fundamental processes in network maintenance.

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There are no labs for this chapter.

Chapter 2 Labs

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