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  • 1. Network+ Guide to Networks Third Edition Chapter 12: Troubleshooting Networking Problems
  • 2. 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 Network + 2
  • 3. 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 Network + 3
  • 4. Troubleshooting Methodology (continued) • Recognize the potential effects of a solution • Implement a solution • Test the solution • Document the solution Network + 4
  • 5. Troubleshooting Methodology (continued) Network + 5
  • 6. Troubleshooting Methodology (continued) • Identify the Symptoms • Access to the network affected • Network performance affected • Data or programs affected • Only certain network services affected Network + 6
  • 7. 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 Network + 7
  • 8. 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? Network + 8
  • 9. 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? Network + 9
  • 10. Troubleshooting Methodology (continued) Network + 10
  • 11. Troubleshooting Methodology (continued) Network + 11
  • 12. 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? Network + 12
  • 13. 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? Network + 13
  • 14. 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? Network + 14
  • 15. 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? Network + 15
  • 16. 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 Network + 16
  • 17. 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 Network + 17
  • 18. 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 Network + 18
  • 19. Troubleshooting Methodology (continued) • Select the Most Probable Cause • Verify Physical Connectivity • Swapping Equipment • If you suspect a problem lies with a network component Network + 19
  • 20. Troubleshooting Methodology (continued) Network + 20
  • 21. 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? Network + 21
  • 22. 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? Network + 22
  • 23. Troubleshooting Methodology (continued) • Recognize the Potential Effects of a Solution • Scope • Tradeoffs • Security • Scalability • Cost • Using Vendor Information Network + 23
  • 24. 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 Network + 24
  • 25. 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 Network + 25
  • 26. Troubleshooting Methodology (continued) • Test the Solution • Document Problems and Solutions • Staff Involved in Troubleshooting • Recording Problems and Resolutions Network + 26
  • 27. 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 Network + 27
  • 28. 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 Network + 28
  • 29. 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 Network + 29
  • 30. 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 Network + 30
  • 31. Troubleshooting Methodology (continued) • Preventing Future Problems • Review the troubleshooting questions and examples • Predict network problems by network maintenance, documentation, security, or upgrades Network + 31
  • 32. 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 Network + 32
  • 33. Troubleshooting Tools (continued) Network + 33
  • 34. Troubleshooting Tools (continued) • Multimeter • Can measure many characteristics of an electric circuit, including its resistance and voltage Network + 34
  • 35. Troubleshooting Tools (continued) Network + 35
  • 36. 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 Network + 36
  • 37. 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 Network + 37
  • 38. Troubleshooting Tools (continued) Network + 38
  • 39. 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 Network + 39
  • 40. 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 Network + 40
  • 41. Troubleshooting Tools (continued) Network + 41
  • 42. 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 Network + 42
  • 43. 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 Network + 43
  • 44. Troubleshooting Tools (continued) • Abnormal data patterns and packets • Local collisions • Late collisions • Runts • Giants Network + 44
  • 45. 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 Network + 45
  • 46. Troubleshooting Tools (continued) Network + 46
  • 47. Troubleshooting Tools (continued) • Wireless Network Testers • Learn about a wireless environment by viewing the wireless network connection properties on your workstation Network + 47
  • 48. Troubleshooting Tools (continued) Network + 48
  • 49. 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 Network + 49
  • 50. 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 Network + 50
  • 51. Troubleshooting Tools (continued) Network + 51
  • 52. 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 Network + 52
  • 53. 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 Network + 53
  • 54. Chapter Summary (continued) • Test your solution • Operate a help desk • Use a software program for documenting • Record details about a problem • Follow up Network + 54
  • 55. Chapter Summary (continued) • Change management system • Tone generator and tone locator • Multimeter • Cable continuity testers • Cable performance tester Network + 55
  • 56. Chapter Summary (continued) • Network monitor • Protocol analyzers • Wireless network testing tools Network + 56