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Chapter 12: Troubleshooting Networking Problems PowerPoint PPT Presentation


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Chapter 12: Troubleshooting Networking Problems. Network+ Guide to Networks Third Edition. Objectives:. Describe the elements of an effective troubleshooting methodology Follow a systematic troubleshooting process to solve networking problems

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Chapter 12: Troubleshooting Networking Problems

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Chapter 12 troubleshooting networking problems l.jpg

Chapter 12: Troubleshooting Networking Problems

Network+ Guide to Networks

Third Edition


Objectives l.jpg

Objectives:

  • Describe the elements of an effective troubleshooting methodology

  • Follow a systematic troubleshooting process to solve networking problems

  • Use a variety of software and hardware tools to diagnose problems

  • Discuss practical issues related to troubleshooting


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Troubleshooting Methodology

  • Identify the Symptoms

  • Identify the Scope of the Problem

  • Establish What Has Changed

  • Determine the Most Probable Cause

    • Verify user competency

    • Re-create the problem

    • Verify physical connectivity

    • Verify logical connectivity


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Troubleshooting Methodology (continued)

  • Recognize the potential effects of a solution

  • Implement a solution

  • Test the solution

  • Document the solution


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Troubleshooting Methodology (continued)


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Troubleshooting Methodology (continued)

  • Identify the Symptoms

    • Access to the network affected

    • Network performance affected

    • Data or programs affected

    • Only certain network services affected


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Troubleshooting Methodology (continued)

  • Identify the Symptoms (continued)

    • If programs are affected, does the problem include one local application, one networked application, or multiple networked applications

    • What specific error messages do users report

    • One user or are multiple users affected

    • Do symptoms manifest themselves consistently


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Troubleshooting Methodology (continued)

  • Identify the Scope of the Problem

    • How many users or network segments are affected?

      • One user or workstation?

      • A workgroup?

      • A department?

      • One location within an organization?

      • An entire organization?


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Troubleshooting Methodology (continued)

  • Identify the Scope of the Problem (continued)

    • When did the problem begin?

      • Has the network, server, or workstation ever worked properly?

      • Did the symptoms appear in the last hour or day?

      • Have the symptoms appeared intermittently for a long time?

      • Do the symptoms appear only at certain times?


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Troubleshooting Methodology (continued)


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Troubleshooting Methodology (continued)


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Troubleshooting Methodology (continued)

  • Establish What Has Changed

    • Did the operating system or configuration on a server, workstation, or connectivity device change?

    • Were new components added to a server, workstation, or connectivity device?

    • Were old components removed from a server, workstation, or connectivity device?

    • Were new users or segments added to the network?


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Troubleshooting Methodology (continued)

  • Establish What Has Changed (continued)

    • Was a server, workstation, or connectivity device moved from its previous location to a new location?

    • Was a server, workstation, or connectivity device replaced?

    • Was new software installed on a server, workstation, or connectivity device?

    • Was old software removed from a server, workstation, or connectivity device?


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify User Competency

    • Re-create the Problem

      • Can you make the symptoms recur every time?

      • If symptoms recur, are they consistent?

      • Can you make the symptoms recur some of the time?

      • Do the symptoms happen only under certain circumstances?


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Re-create the Problem (continued)

      • In the case of software malfunctions, are the symptoms consistent no matter how many and which programs or files the user has open?

      • Do the symptoms ever happen when you try to repeat them?


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify Physical Connectivity

      • Symptoms of Physical Layer Problems

        • Lengths exceed standards

        • Noise affecting a signal

        • Improper connections

        • Damaged cables

        • Faulty NICs


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify Physical Connectivity

      • Diagnosing Physical Layer Problems

        • Device turned on

        • NIC properly inserted

        • Device’s network cable properly connected

        • Patch cables properly connect


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify Physical Connectivity

      • Diagnosing Physical Layer Problems (continued)

        • Hub, router, or switch properly connected to the backbone

        • Cables in good condition

        • Connectors in good condition and properly seated

        • Network lengths conform to specifications?

        • Devices configured properly


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify Physical Connectivity

      • Swapping Equipment

        • If you suspect a problem lies with a network component


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Troubleshooting Methodology (continued)


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify Logical Connectivity

      • Do error messages reference damaged or missing files or device drivers?

      • Do error messages reference malfunctioning or insufficient resources (such as memory)?

      • Has an operating system, configuration, or application been recently changed, introduced, or deleted?

      • Does the problem occur with only one application or a few, similar applications?


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Troubleshooting Methodology (continued)

  • Select the Most Probable Cause

    • Verify Logical Connectivity

      • Does the problem happen consistently?

      • Does the problem affect a single user or one group of users?


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Troubleshooting Methodology (continued)

  • Recognize the Potential Effects of a Solution

    • Scope

    • Tradeoffs

    • Security

    • Scalability

    • Cost

    • Using Vendor Information


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Troubleshooting Methodology (continued)

  • Implement a Solution

    • Implement a safe and reliable solution:

      1. Collect documentation about a problem’s symptoms

      2. Backup existing software and keep the old parts handy

      3. Perform the change and record your actions

      4. Test your solution


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Troubleshooting Methodology (continued)

  • Implement a Solution

    • Implement a safe and reliable solution:

      5. Before leaving the area clean it up

      6. Record the details you have collected about the symptoms, the problem, and the solution

      7. If solution involved a significant change or problem, revisit the solution a day or two later to verify that the problem has been solved


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Troubleshooting Methodology (continued)

  • Test the Solution

  • Document Problems and Solutions

    • Staff Involved in Troubleshooting

    • Recording Problems and Resolutions


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Troubleshooting Methodology (continued)

  • A typical problem record form should include

    • The name, department, and phone number of the problem originator

    • Information regarding whether the problem is software- or hardware-related

    • If the problem is software-related, the package to which it pertains; if the problem is hardware-related, the device or component to which it pertains


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Troubleshooting Methodology (continued)

  • A typical problem record form should include (continued)

    • Symptoms of the problem, including when it was first noticed

    • The name and telephone number of the network support contact

    • The amount of time spent troubleshooting the problem

    • The resolution of the problem


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Troubleshooting Methodology (continued)

  • Notifying Others of Changes

    • A change management system

      • Adding or upgrading software

      • Adding or upgrading hardware or other devices

      • Adding new hardware

      • Changing the properties of a network device


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Troubleshooting Methodology (continued)

  • A change management system (continued)

    • Increasing or decreasing rights

    • Physically moving networked devices

    • Moving user accounts and their files/directories

    • Making changes in processes

    • Making changes in vendor policies or relationships


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Troubleshooting Methodology (continued)

  • Preventing Future Problems

    • Review the troubleshooting questions and examples

    • Predict network problems by network maintenance, documentation, security, or upgrades


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Troubleshooting Tools

  • Crossover Cable

    • Use to directly interconnect two nodes

  • Tone Generator and Tone Locator

    • Tone generator is a small electronic device that issues a signal on a wire pair

    • Tone locator is a device that emits a tone when it detects electrical activity on a wire pair


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Troubleshooting Tools (continued)


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Troubleshooting Tools (continued)

  • Multimeter

    • Can measure many characteristics of an electric circuit, including its resistance and voltage


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Troubleshooting Tools (continued)


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Troubleshooting Tools (continued)

  • Use a multimeter to:

    • Verify that a cable is properly conducting electricity

    • Check for the presence of noise on a wire

    • Verify that the amount of resistance on coaxial cable

    • Test for short or open circuits in the wire


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Troubleshooting Tools (continued)

  • Cable Continuity Testers

    • In troubleshooting a Physical layer problem, you may find the cause of a problem by simply testing whether your cable is carrying a signal to its destination


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Troubleshooting Tools (continued)


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Troubleshooting Tools (continued)

  • Cable Performance Testers

    • Measure the distance to a connectivity device, termination point, or cable fault

    • Measure attenuation along a cable

    • Measure near-end crosstalk between wires

    • Measure termination resistance and impedance


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Troubleshooting Tools (continued)

  • Cable Performance Testers (continued)

    • Issue pass/fail ratings for CAT 3, CAT 5, CAT 5e, CAT 6, or CAT 7 standards

    • Store and print cable testing results or directly save data to a computer database

    • Graphically depict a cable’s attenuation and crosstalk characteristics over the length of the cable


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Troubleshooting Tools (continued)


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Troubleshooting Tools (continued)

  • Network Monitors

    • Continuously monitor network traffic on a segment

    • Capture network data transmitted on a segment

    • Capture frames sent to or from a specific node

    • Reproduce network conditions

    • Generate statistics about network activity


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Troubleshooting Tools (continued)

  • Network Monitors (continued)

    • Discover all network nodes on a segment

    • Establish a baseline that reflects network traffic

    • Store traffic data and generate reports

    • Trigger alarms when traffic conditions meet preconfigured conditions


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Troubleshooting Tools (continued)

  • Abnormal data patterns and packets

    • Local collisions

    • Late collisions

    • Runts

    • Giants


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Troubleshooting Tools (continued)

  • Abnormal data patterns and packets (continued)

    • Jabber

    • Negative frame sequence checks

    • Ghosts

  • Protocol Analyzers

    • Can capture traffic

    • Can also analyze frames

    • To Layer 7 of the OSI Model


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Troubleshooting Tools (continued)


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Troubleshooting Tools (continued)

  • Wireless Network Testers

    • Learn about a wireless environment by viewing the wireless network connection properties on your workstation


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Troubleshooting Tools (continued)


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Troubleshooting Tools (continued)

  • Wireless network testing tools

    • Identify transmitting APs, stations and channels

    • Measure signal strength and range

    • Indicate the effects of attenuation, signal loss, and noise

    • Interpret signal strength information


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Troubleshooting Tools (continued)

  • Wireless network testing tools (continued)

    • Ensure proper association and reassociation

    • Capture and interpret traffic

    • Measure throughput and assess data

    • Analyze the characteristics of each channel


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Troubleshooting Tools (continued)


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Chapter Summary

  • Before you can resolve a network problem, you need to determine its cause

  • Act like a doctor diagnosing a patient

  • Identify the scope of the problem

  • At each point, stop to consider

  • Ensure that the user is performing all functions correctly


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Chapter Summary (continued)

  • Attempt to reproduce the problem’s symptoms

  • Check for sound connections

  • Exchange component for a functional one

  • Determine properly configured software

  • Consult vendor information


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Chapter Summary (continued)

  • Test your solution

  • Operate a help desk

  • Use a software program for documenting

  • Record details about a problem

  • Follow up


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Chapter Summary (continued)

  • Change management system

  • Tone generator and tone locator

  • Multimeter

  • Cable continuity testers

  • Cable performance tester


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Chapter Summary (continued)

  • Network monitor

  • Protocol analyzers

  • Wireless network testing tools


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