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Network+ Guide to Networks 5 th Edition. Chapter 13 Troubleshooting Network Problems. Objectives. Describe the steps involved in an effective troubleshooting methodology Follow a systematic troubleshooting process to identify and resolve networking problems

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network guide to networks 5 th edition

Network+ Guide to Networks5th Edition

Chapter 13

Troubleshooting Network Problems

objectives
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

Network+ Guide to Networks, 5th Edition

troubleshooting methodology
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

Network+ Guide to Networks, 5th Edition

troubleshooting methodology cont d
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

Network+ Guide to Networks, 5th Edition

identify the symptoms and problems
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

Network+ Guide to Networks, 5th Edition

identify the affected area
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?

Network+ Guide to Networks, 5th Edition

identify the affected area cont d
Identify the Affected Area (cont’d.)
  • 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

Network+ Guide to Networks, 5th Edition

identify the affected area cont d8
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

Network+ Guide to Networks, 5th Edition

slide9

Figure 13-1 Identifying the area affected by a problem

Network+ Guide to Networks, 5th Edition

determine what has changed
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

Network+ Guide to Networks, 5th Edition

establish the most probable cause
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

Network+ Guide to Networks, 5th Edition

establish the most probable cause cont d
Establish the Most Probable Cause (cont’d.)
  • 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

Network+ Guide to Networks, 5th Edition

establish the most probable cause cont d14
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

Network+ Guide to Networks, 5th Edition

establish the most probable cause cont d15
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, 5th Edition

slide16

Figure 13-3 Verifying physical connectivity

Network+ Guide to Networks, 5th Edition

establish the most probable cause cont d17
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, 5th Edition

determine whether escalation is necessary
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

Network+ Guide to Networks, 5th Edition

create an action plan and solution including potential effects
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

Network+ Guide to Networks, 5th Edition

create an action plan and solution including potential effects cont d
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

Network+ Guide to Networks, 5th Edition

create an action plan and solution including potential effects cont d21
Create an Action Plan and Solution Including Potential Effects (cont’d.)
  • 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

Network+ Guide to Networks, 5th Edition

create an action plan and solution including potential effects cont d22
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

Network+ Guide to Networks, 5th Edition

implement and test the solution
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

Network+ Guide to Networks, 5th Edition

implement and test the solution cont d
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

Network+ Guide to Networks, 5th Edition

identify the results and effects of the solution
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

Network+ Guide to Networks, 5th Edition

document the solution and process
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

Network+ Guide to Networks, 5th Edition

document the solution and process cont d
Document the Solution and Process (cont’d.)
  • 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
  • Supported services list document
    • Lists all supported service, software and contacts
  • Follow-up with user

Network+ Guide to Networks, 5th Edition

document the solution and process cont d28
Document the Solution and Process (cont’d.)
  • 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

Network+ Guide to Networks, 5th Edition

help to prevent future problems
Help to Prevent Future Problems
  • Avert network problems
    • Network maintenance
    • Documentation
    • Security
    • Upgrades

Network+ Guide to Networks, 5th Edition

troubleshooting tools
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

Network+ Guide to Networks, 5th Edition

crossover cable
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

Network+ Guide to Networks, 5th Edition

tone generator and tone locator
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

Network+ Guide to Networks, 5th Edition

tone generator and tone locator cont d
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

Network+ Guide to Networks, 5th Edition

multimeter
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

Network+ Guide to Networks, 5th Edition

multimeter cont d
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, 5th Edition

multimeter cont d37
Multimeter (cont’d.)
  • Multimeter
    • Separate instruments for measuring wires impedance, resistance, voltage
    • Has several uses
    • Sophistication, features, and costs vary

Network+ Guide to Networks, 5th Edition

multimeter cont d38

Figure 13-5 A multimeter

Multimeter (cont’d.)

Network+ Guide to Networks, 5th Edition

cable continuity testers
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

Network+ Guide to Networks, 5th Edition

cable continuity testers cont d
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

Network+ Guide to Networks, 5th Edition

cable performance testers
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, 5th Edition

cable performance testers cont d
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

Network+ Guide to Networks, 5th Edition

voltage event recorders
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

Network+ Guide to Networks, 5th Edition

butt set
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

Network+ Guide to Networks, 5th Edition

butt set cont d

Figure 13-9 Butt set

Butt Set (cont’d.)

Network+ Guide to Networks, 5th Edition

network monitors
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, 5th Edition

network monitors cont d
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

Network+ Guide to Networks, 5th Edition

protocol analyzers
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

Network+ Guide to Networks, 5th Edition

protocol analyzers cont d53
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

Network+ Guide to Networks, 5th Edition

wireless network testers
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

Network+ Guide to Networks, 5th Edition

wireless network testers cont d
Wireless Network Testers (cont’d.)
  • Commercial tools advantages
    • Portability
    • Installed with wireless network analysis tools
    • Contain more powerful antennas

Network+ Guide to Networks, 5th Edition

summary
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, 5th Edition