Troubleshooting Physical Networks (5.1 & 5.2) Flashcards
Network Troubleshooting Methodology
- Identify the problem
- Establish a theory to determine the cause
- Test the theory to determine the cause
- Establish a plan of action to resolve the problem and identify potential effects
- Implement the solution or escalate as necessary
- Verify the whole system functionality and if applicable, implement preventive
measures - Document findings, actions, outcomes, and lesson learned
▪ Gather more details
▪ Identify symptoms
▪ Check for changes
▪ Duplicate problem
How to implement the network troubleshooting methodology
o Approach multiple problems individually
▪ Top-to-bottom
▪ Bottom-to-top
▪ Divide and conquer
o If confirmed, determine next steps
o If unconfirmed, reestablish new theory or escalate
Cable Review
VERY IMPORTANT( CHECK THE PICTURE)
Coaxial
▪ 100 Mbps, 500 meters
Coaxial Twinaxial
▪ 10 Gbps, 5 meters
▪ 100 Gbps, 7 meters
MORE PICTURES
Tip:
Protecting your network from electromagnetic interference (EMI)
▪ The extra shielding helps protect the STP cables from EMI and power
frequency interruptions
▪ Fiber cables are immune to EMI
Plenum Cable
▪ Used when running cables horizontally in a building across a particular
level
Riser Cable
▪ Used to run network cables vertically between floors in a building in a
cable riser or elevator shaft
▪ Riser cables cannot be used in plenum spaces since they are not made
from PVC or FEP
Rollover/Console Cable
o A type of null-modem cable that is used to connect a
computer terminal to a router’s console port
Crossover Cable
o Connects two Ethernet network devices directly, such as
two computers without a switch or a router in between
Power Over Ethernet (or PoE)
o Passes electric power over twisted pair Ethernet cable to
powered devices
o PoE provides 15.4 to 60 watts of power using two twisted
pairs, and between 60-100 watts of power using all four
Snips or Cutters
▪ Used to simply cut a piece of cable off a larger spool or run of cable
▪ Looks a lot like a pair of scissors, but uses stronger blades to cut twisted
copper cables, coaxial, cables, or even larger cable bundles
Cable strippers
▪ Strips the end of the cable to prepare it the attachment of a RJ-45 or
other type of connector
Cable Crimper
▪ Used to attach the connector to the end of the cable
▪ support both RJ-45 and RJ-11 connectors
▪ If you are working with coaxial cables, then you will need a cable crimper
that supports an RG-6 or RG-59 connector
Cable Tester
▪ Verifies continuity for each wire in the cable to ensure there are no
breaks
▪ Verifies the pinouts of the connectors
▪ Different testers for different cable types
Multi-tester
▪ Supports not just ethernet cables using RJ-45, but also BNC connectors
for coaxial cables, as well as IDE, PATA, SATA, RJ-45, fiber, DB25, DB9s
and anything else that you might need to test
Wire Map tool
▪ Like a cable tester, but it works specifically for twisted pair ethernet
cables
▪ It can diagnose any issues with that cable
Open Pair
o Occurs when one or more of the conductors in the pair are
not connected to a pin at one or the other end
Short Pair
o Occurs when the conductors of a wire pair are connected
to each other at any location in the cable
Short Between Pairs
o Occurs when the conductors of two wires in different pairs
are connected at any location in the cable
Reversed Pair
o Occurs when the two wires in a single pair are connected
to the opposite pins of the pair at the other end of the
cable
Crossed Pairs
o Occur when both wires of one color pair are connected to
the pins of a different color pair at the opposite end
Split Pairs
o Occur when the wire from one pair is split away from the
other and crosses over a wire in an adjacent pair
Cable Certifier
▪ Used with an existing cable to determine its Category or data throughput
Multimeter
▪ Checks the voltage or the amperage or the resistance of a copper cable
▪ Used to verify if a cable is broken or not
▪ Used to check coaxial cables to ensure there is no cuts or breaks in the
middle of a patch cable, or test power sources or power cords
Multimeter
▪ Checks the voltage or the amperage or the resistance of a copper cable
▪ Used to verify if a cable is broken or not
▪ Used to check coaxial cables to ensure there is no cuts or breaks in the
middle of a patch cable, or test power sources or power cords
Punch-Down Tool
▪ Used to terminate wires on a punch-down block without stripping off the
insulation
▪ Used with 66 block or 110 block, network jacks, and patch panels
Toner Generator/Probe
▪ Allows technicians to generate a tone at one end of a connection and use
the probe to audibly detect the wire pair connected to the tone
generator
▪ Often called a “Fox and Hound”
▪ Fox is a tone generator
▪ Hound is a toner probe
Loopback Adapter
▪ Connects transmit pins (or fibers) to receive pins (or fiber) to test a network interface ● Ethernet Pinout o Pins 1 to 3 (Tx+ to Rx+) o Pins 2 to 6 (Tx- to Rx-) ● Fiber o Transmit fiber to Receive fiber o Used with diagnostic software to test Ethernet connectivity of a client
Time-domain Reflectometer (TDR)
▪ Locate breaks in a copper cable and provide an estimate of the severity
and the distance to the break
● Optical Time-domain Reflectometer (OTDR)
o Used for fiber optic cables
Fiber Light Meter
▪ A device that provides a continuous wave of stable source of energy for
attenuation measurements
Fusion Splicer
▪ A machine that is used to permanently join two fibers together
Tap
▪ A simple device that connects directly to the cabling infrastructure to
split or copy packets for use in analysis, security, or general network
management
▪ Spectrum analyzer is a device that measures and displays signal
amplitude (strength) as it varies by frequency within its frequency range (spectrum)
Attenuation
▪ Loss of signal strength on a network cable or connection over the length
of the cable
▪ Twisted pair cables can transmit data over a maximum distance of 100
meters
▪ Coaxial cables can transmit data over a maximum distance of 500 meters
● Frequency
● Noise
● Physical surroundings
▪ The higher the frequency, the higher the bandwidth
▪ Noise
● Additional electrical or radio frequency noise in the areas where
your network cables are operating
o Use the proper cables for the physical environment you
are operating in
o Shorten the distance
o Use an amplifier or repeater
▪ Clean and polish both ends of fiber cable and connectors or switch to a
cable with higher quality
Interference
▪ Occurs when multiple cables in the same frequency band are operating in
close proximity to each other
▪ Use high quality twisted pair cables or higher category rated cables
▪ Plan cable runs to operate in parallel to any high power cables
Decibel (dB) Loss
▪ Measures the amount of signal deterioration we are experiencing on a given connection ● Copper o decrease in voltage ● Fiber o amount of lost light
Copper Cable Issues
o There are many types of issues that could occur withing your copper cables
▪ Incorrect pinouts
● By default, the patch panel should use the TIA-568B pinout, with
pins 1 through 8 being connected as:
o White/Orange – Orange – White/Green – Blue –
White/Blue – Green – White/Brown – Brown
Bad port
● If you suspect a bad port on a switch or router, you should
connect a loopback plug to the port on that device and run a test
using specialized software
Open
● There is nothing on the other end of the connection or there’s a
break in the wires between the source and the destination
Short
● Indicates there are two wires are connected together somewhere
in the connection
Transceiver
▪ A transmitter and a receiver combined into a single device that converts a
network connection from one type to another
▪ They are designed to support a certain type of connection and a certain
cable type
Dry Cleaning
▪ Using light pressure while rubbing the end face of a fiber cable or
connector with a dry-cleaning cloth in one direction
Wet Cleaning
▪ Moistening a piece of lint-free cloth with a fiber optic cleaning solution
and wiping the end face of the cable or connector
Duplex Mismatch
▪ When one device thinks the connection is full duplex and the other thinks
it is half duplex
▪ Ensure both devices are configured to auto negotiate the connection
properly
