Chapter 12: Troubleshooting Networking Problems

1. Chapter 12: Troubleshooting Networking Problems Network+ Guide to Networks Third Edition

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

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

4. Troubleshooting Methodology (continued) • Recognize the potential effects of a solution • Implement a solution • Test the solution • Document the solution

5. Troubleshooting Methodology (continued)

6. Troubleshooting Methodology (continued) • Identify the Symptoms • Access to the network affected • Network performance affected • Data or programs affected • Only certain network services affected

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

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?

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?

10. Troubleshooting Methodology (continued)

11. Troubleshooting Methodology (continued)

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?

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?

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?

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?

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

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

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

19. Troubleshooting Methodology (continued) • Select the Most Probable Cause • Verify Physical Connectivity • Swapping Equipment • If you suspect a problem lies with a network component

20. Troubleshooting Methodology (continued)

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?

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?

23. Troubleshooting Methodology (continued) • Recognize the Potential Effects of a Solution • Scope • Tradeoffs • Security • Scalability • Cost • Using Vendor Information

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

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

26. Troubleshooting Methodology (continued) • Test the Solution • Document Problems and Solutions • Staff Involved in Troubleshooting • Recording Problems and Resolutions

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

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

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

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

31. Troubleshooting Methodology (continued) • Preventing Future Problems • Review the troubleshooting questions and examples • Predict network problems by network maintenance, documentation, security, or upgrades

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

33. Troubleshooting Tools (continued)

34. Troubleshooting Tools (continued) • Multimeter • Can measure many characteristics of an electric circuit, including its resistance and voltage

35. Troubleshooting Tools (continued)

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

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

38. Troubleshooting Tools (continued)

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

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

41. Troubleshooting Tools (continued)

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

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

44. Troubleshooting Tools (continued) • Abnormal data patterns and packets • Local collisions • Late collisions • Runts • Giants

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

46. Troubleshooting Tools (continued)

47. Troubleshooting Tools (continued) • Wireless Network Testers • Learn about a wireless environment by viewing the wireless network connection properties on your workstation

48. Troubleshooting Tools (continued)

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

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