Transcript Lec5_ NET 311H

Organized by: Nada Alhirabi
NET 311
Lec4:
Troubleshooting Network Problems
Network+ Guide to Networks
5th 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
• Document symptoms, solutions, and results when
troubleshooting network problems
• Use a variety of software and hardware tools to
diagnose problems
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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 Troubleshooting
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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:
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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 Troubleshooting
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Troubleshooting Methodology
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Proceed logically and methodically
Follow recommended steps
Use experience when necessary
Logical approach benefits
– Prevents wasteful, time-consuming efforts
• Unnecessary software, hardware replacements
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Troubleshooting Methodology (cont’d.)
• Troubleshooting steps
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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
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Help to Prevent Future Problems
• Avert network problems
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Network maintenance
Documentation
Security
Upgrades
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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
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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
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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
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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
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Tone Generator and Tone Locator
(cont’d.)
Figure 13-4 Use of a tone generator and tone locator
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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
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Multimeter (cont’d.)
• Resistance
– Fundamental wire property
• Dependent on wire’s molecular structure, size
– Measured in ohms
• Using ohmmeter
• Impedance
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Resistance contributing to controlling signal
Measured in ohms
Telltale factor for ascertaining where cable faults lie
Some required for proper signal transmission and
interpretation
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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
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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
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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
• Offer convenience: portable, lightweight,
low cost
Figure 13-6 Cable
continuity testers
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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
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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
Figure 13-7 A cable
performance tester
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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
Figure 13-8 Voltage event
recorder
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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
Figure 13-9 Butt
set
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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
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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
Figure 13-10 Traffic
captured by a protocol
analyzer
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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
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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
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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
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Summary
• Methodical, logical troubleshooting methodology
– Key to solving network problems
• Troubleshooting tools
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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
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