1. Lec4: Troubleshooting Network Problems Network+ Guide to Networks 5 th Edition Chapter 13 Troubleshooting Network Problems Organized by: Nada Alhirabi NET 311

2. Network+ Guide to Networks, 5 th Edition2 Objectives Describe the steps involved in an effective troubleshooting methodology Follow a systematic troubleshooting process to identify and resolve networking problems Document symptoms, solutions, and results when troubleshooting network problems Use a variety of software and hardware tools to diagnose problems

3. Definition - What does Network Troubleshooting mean? Network troubleshooting is the collective measures and processes used to identify, diagnose and resolve problems and issues within a computer network. It is a systematic process that aims to resolve problems and restore normal network operations within the network. Network troubleshooting can be a manual or automated task. When using automated tools, network management can be done using network diagnostic software. Techopedia explains Network Troubleshooting3

4. Network Troubleshooting Network troubleshooting is primarily done by network engineers or administrators to repair or optimize a network. It is generally done to recover and establish network or Internet connections on end nodes/devices. Some of the processes within network troubleshooting include but are not limited to: –Finding and resolving problems and establishing Internet/network connection of a computer/device/node –Configuring a router, switch or any network management device –Installing cables or Wi-Fi devices –Updating firmware devices on router switch –Removing viruses –Adding, configuring and reinstalling a network printer Techopedia explains Network Troubleshooting4

5. Network+ Guide to Networks, 5 th Edition5 Troubleshooting Methodology Proceed logically and methodically Follow recommended steps Use experience when necessary Logical approach benefits –Prevents wasteful, time-consuming efforts Unnecessary software, hardware replacements

6. Network+ Guide to Networks, 5 th Edition6 Troubleshooting Methodology (cont’d.) Troubleshooting steps –Identify symptoms, problems –Identify affected area –Determine what has changed –Establish most probable cause –Determine if escalation necessary –Create action plan, solution –Implement solution, test result –Identify results, effects –Document solution, process

7. Network+ Guide to Networks, 5 th Edition7 Identify the Symptoms and Problems Ask questions –Answers help identify network problem symptoms Avoid jumping to conclusions about symptoms Pay attention –Users, system and network behaviors, and error messages –Treat each symptom uniquely

8. Network+ Guide to Networks, 5 th Edition8 Identify the Affected Area Determine affected area and group –One user or workstation? –A workgroup? –A department? –One location within an organization? –An entire organization? Narrow down time frame –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 of the day, week, month, or year? Benefits –Eliminates some causes; points to other

9. Network+ Guide to Networks, 5 th Edition9 Identify the Affected Area (cont’d.) Take time to troubleshoot correctly –Ask specific questions Identify problem scope –Filter unrelated user information Discover time and frequency of problem –May reveal more subtle network problems Identify affected problem area –Leads to next troubleshooting steps

10. Network+ Guide to Networks, 5 th Edition10 Figure 13-1 Identifying the area affected by a problem

11. Network+ Guide to Networks, 5 th Edition11 Figure 13-2 Identifying the chronological scope of a problem

12. Network+ Guide to Networks, 5 th Edition12 Determine What Has Changed Become aware of recent network changes –Ask questions pinpointing problem resulting from network change Possible actions if change generated problem –Correct problem –Reverse change Less risky, less time consuming Network change records –Track what has changed Make records available to staff members

13. Network+ Guide to Networks, 5 th Edition13 Establish the Most Probable Cause Close to determining problem cause Verify user competency Ensure human error is not problem source Verify user is performing network tasks correctly –Watch –Connect using remote desktop software –Talk over phone Results Catch user-generated mistakes Gain clues for further troubleshooting Re-create the problem Learn more about problem causes Reproduce symptoms –Log on as user; log on under privileged account –Follow same steps –Ask questions Determine whether problem symptoms reproducible, to what extent Ask user precisely what was done before error

14. Network+ Guide to Networks, 5 th Edition14 Establish the Most Probable Cause (cont’d.) Verify Physical layer connectivity –Half of all network problems occur at Physical layer –Symptoms of Physical layer problems Segment, network lengths exceed standards Noise Improper terminations, faulty connectors, loose connectors, poorly crimped connections Damaged cables Faulty NICs –Software errors may point to physical connectivity problem

15. Establish the Most Probable Cause (cont’d.) Verify Physical layer connectivity (cont’d.) –Diagnosing Physical layer Problems Ask questions Verify connections between devices Verify soundness of connection hardware –Swapping equipment: tests theories Exchange faulty component for functional one Change patch cable Better option: build in redundancy Network+ Guide to Networks, 5 th Edition15

16. Network+ Guide to Networks, 5 th Edition16 Figure 13-3 Verifying physical connectivity

17. Establish the Most Probable Cause (cont’d.) Verify logical connectivity –Review questions identifying logical connectivity problem –Logical connectivity problems more difficult to isolate, resolve than physical connectivity problems –Software-based causes Resource conflicts with NICs configuration Improperly configured NIC Improperly installed, configured client software Improperly installed, configured network protocols, services Network+ Guide to Networks, 5 th Edition17

18. Network+ Guide to Networks, 5 th Edition18 Determine Whether Escalation is Necessary Help desks –Help desk analysts Proficient in basic workstation, network troubleshooting First-level support –Network specialist Second-level support –Help desk coordinator Third-level support personnel Know when and how to escalate –Follow given procedure

19. Network+ Guide to Networks, 5 th Edition19 Create an Action Plan and Solution Including Potential Effects Consider how solution affects users, network functionality Scope –Assess solution’s scope Before implementing solution –Wait if not an emergency Trade-offs –Restore functionality for one user group May remove functionality for others

20. Network+ Guide to Networks, 5 th Edition20 Create an Action Plan and Solution Including Potential Effects (cont’d.) Security –Be aware of inadvertent security implications Network access, resource privileges addition or removal consequences –Before upgrade, patch installation Understand access changes for authorized, unauthorized users Scalability –Solution types Position network for future additions, enhancements Temporary fix organization will outgrow Cost –Weigh options carefully –Consider poor network performance identification Address those areas separately

21. Network+ Guide to Networks, 5 th Edition21 Create an Action Plan and Solution Including Potential Effects (cont’d.) Use vendor information –Manufacturer documentation –Free online troubleshooting information Searchable databases Sophisticated web interfaces for troubleshooting their equipment Vendor’s technical phone support Consult with others, within, outside your organization

22. Network+ Guide to Networks, 5 th Edition22 Implement and Test the Solution Implement only after proposed solution’s effects researched Implementation –Brief or long –Requires foresight, patience –Use methodical and logical approach Leads to efficient correction process Unless major problem – fix as quickly as possible –Follow series of steps Implement a safe, reliable solution

23. Network+ Guide to Networks, 5 th Edition23 Implement and Test the Solution (cont’d.) Roll out solution in stages –Especially in large-scale fixes After solution implementation –Verify problem solved properly –Testing dependencies Solution itself Area affected by problem Inability to test immediately

24. Network+ Guide to Networks, 5 th Edition24 Identify the Results and Effects of the Solution After testing solution implementation –Determine how and why solution was successful –Determine solution’s effect on users and functionality –Avoid creating unintended, negative consequences –Communicate solution to colleagues

25. Network+ Guide to Networks, 5 th Edition25 Document the Solution and Process Always record: –Problem symptoms and cause (or causes) –Solution Justification for recording –Impossible to remember each incident’s circumstances –Job changes Use centrally located database –Accessible to all networking personnel Call tracking system (help desk software) –User-friendly, graphical Prompts for problem information –Assigns unique problem number –Highly customizable –If not available, use simple electronic form

26. Network+ Guide to Networks, 5 th Edition26 Document the Solution and Process (cont’d.) Supported services list document –Lists all supported service, software and contacts Follow-up with user Notify others of changes –Record resolution in call tracking system –Communication Alerts others about problem, solution Notifies others of network changes made –Many types of changes to record Not necessary to record minor modifications

27. Network+ Guide to Networks, 5 th Edition27 Help to Prevent Future Problems Avert network problems –Network maintenance –Documentation –Security –Upgrades

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29. Network+ Guide to Networks, 5 th Edition29 Troubleshooting Tools Utilities help troubleshoot network problems –Ping –Specialized tools Specifically designed to analyze, isolate network problems Simple continuity testers Protocol analyzers –Tool selection dependencies Problem being investigated Network characteristics

30. Network+ Guide to Networks, 5 th Edition30 Crossover Cable Crossover cable –Reverses transmit and receive wire pairs in one connector Directly interconnect two nodes without intervening connectivity device –Use Verify NIC transmitting, receiving signals properly

31. Network+ Guide to Networks, 5 th Edition31 Tone Generator and Tone Locator Ideal situation –Telecommunications closet ports, wire terminations all labeled properly Reality –Telecommunications closet disorganized, poorly documented Tone generator (toner) –Issues signal on wire pair

32. Network+ Guide to Networks, 5 th Edition32 Tone Generator and Tone Locator (cont’d.) Tone locator (probe) –Emits tone when electrical activity detected Probe kit –Generator and locator combination –Fox and hound Testing requires trial and error Use –Determine where wire pair terminates Not used to determine cable characteristics

33. Network+ Guide to Networks, 5 th Edition33 Tone Generator and Tone Locator (cont’d.) Figure 13-4 Use of a tone generator and tone locator

34. Network+ Guide to Networks, 5 th Edition34 Multimeter Tests cables for faults –Isolates problems with network cables Multimeter –Measures electric circuit characteristics Resistance and voltage Voltmeter –Measures electric circuit pressure, voltage Voltage creates signals over network wire

35. Multimeter (cont’d.) Resistance –Fundamental wire property Dependent on wire’s molecular structure, size –Measured in ohms Using ohmmeter Impedance –Resistance contributing to controlling signal –Measured in ohms –Telltale factor for ascertaining where cable faults lie –Some required for proper signal transmission and interpretation Network+ Guide to Networks, 5 th Edition35

36. Network+ Guide to Networks, 5 th Edition36 Multimeter (cont’d.) Multimeter –Separate instruments for measuring wires impedance, resistance, voltage –Has several uses –Sophistication, features, and costs vary Figure 13-5 A multimeter

37. Network+ Guide to Networks, 5 th Edition37 Cable Continuity Testers Cable checkers (continuity testers, cable testers) –Tests whether cable carrying signal to destination –Tests cable continuity Copper-based cable tester –Consists of two parts Base unit generates voltage Remote unit detects voltage Series of lights, audible tone –Signal pass/fail

38. Network+ Guide to Networks, 5 th Edition38 Cable Continuity Testers (cont’d.) Verify UTP, STP wires paired correctly –Not shorted, exposed, crossed Fiber optic continuity tester –Issues light pulses on fiber –Determines whether pulses reached other end –Tests the cable Test all cables to ensure meeting network’s required standards –Homemade or purchased Offer convenience: portable, lightweight, low cost Figure 13-6 Cable continuity testers

39. Cable Performance Testers Determines if cable carrying current Continuity testers versus performance testers –Sophistication and price –Performance tester accomplishes same continuity, fault tests –Continuity testers perform additional tasks Sophisticated performance testers –Include TDR (time domain reflectometer) Issue signal, measures signal bounce back Indicate proper terminator installation, function, node distance Network+ Guide to Networks, 5 th Edition39

40. Network+ Guide to Networks, 5 th Edition40 Cable Performance Testers (cont’d.) Fiber-optic connections testers –Use OTDRs (optical time domain reflectometers) Transmit light-based signals of different wavelengths over fiber –OTDRs Measure fiber length Determine faulty splice locations, breaks, connectors, bends Measure attenuation over cable Expensive Figure 13-7 A cable performance tester

41. Network+ Guide to Networks, 5 th Edition41 Voltage Event Recorders Voltage event –Any condition where voltage exceeds or drops below predefined levels Voltage event recorder –Collects data about power quality Downloaded to workstation Analyzed by software –Cost up to $5000 Figure 13-8 Voltage event recorder

42. Network+ Guide to Networks, 5 th Edition42 Butt Set Lineman’s handset, telephone test set –Butt into telephone conversation –Rugged, sophisticated telephone Uses –Determine if line functioning Receiving signal, picking up noise affecting signal –Sophisticated butt sets Perform rudimentary cable testing –Detecting dial tone on line Figure 13-9 Butt set

43. Network Monitors Software-based tool –Continually monitors network traffic from server, workstation attached to network –Interprets up to Layer 3 –Determine protocols passed by each frame –Cannot interpret frame data Included in NOS –Microsoft’s Network Monitor Purchase or free download tools developed by other software companies –All use similar graphical interfaces Network+ Guide to Networks, 5 th Edition43

44. Network+ Guide to Networks, 5 th Edition44 Network Monitors (cont’d.) Network adapter –Must support promiscuous mode Common terms for abnormal data patterns, packets –Local collisions –Late collisions –Runts –Giants –Jabber –Negative frame sequence checks –Ghosts

45. Network+ Guide to Networks, 5 th Edition45 Protocol Analyzers Protocol analyzer (network analyzer) –Captures traffic, analyzes frames Typically to Layer 7 Variety of protocol analyzer software available –Wireshark Same features as network monitor –Few extras –Generates traffic Sniffer (packet sniffer) hardware –Older term Figure 13-10 Traffic captured by a protocol analyzer

46. Network+ Guide to Networks, 5 th Edition46 Protocol Analyzers (cont’d.) Offers versatility in information type, depth –Could collect more information than can be reasonably processed –Set filters to avoid Before using network monitor or protocol analyzer –Learn what network traffic normally looks like Capture data for time period on regular basis

47. Network+ Guide to Networks, 5 th Edition47 Wireless Network Testers Tools containing wireless NICs, running wireless protocols Workstation wireless network connection properties –Shows a little about wireless environment Connection duration, signal speed and strength, number of packets exchanged –Only applies to one workstation Programs scan for wireless signals –Discover access points, wireless stations transmitting –Free

48. Network+ Guide to Networks, 5 th Edition48 Wireless Network Testers (cont’d.) Commercial tools advantages –Portability –Installed with wireless network analysis tools –Contain more powerful antennas Figure 13-11 Wireless network testing tool

49. Summary Methodical, logical troubleshooting methodology –Key to solving network problems Troubleshooting tools –Tone generator and tone locator –Multimeters –Basic cable continuity testers –Cable performance tester –Voltage event recorder –Butt set –Network monitors and protocol analyzers –Wireless network testing tools Network+ Guide to Networks, 5 th Edition49