Troubleshooting Physical Networks (5.1 & 5.2)

Question 1

Network Troubleshooting Methodology

Answer 1

1. Identify the problem
2. Establish a theory to determine the cause
3. Test the theory to determine the cause
4. Establish a plan of action to resolve the problem and identify potential effects
5. Implement the solution or escalate as necessary
6. Verify the whole system functionality and if applicable, implement preventive
   measures
7. Document findings, actions, outcomes, and lesson learned
   ▪ Gather more details
   ▪ Identify symptoms
   ▪ Check for changes
   ▪ Duplicate problem

Question 2

How to implement the network troubleshooting methodology

Answer 2

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

Question 3

Cable Review

Answer 3

VERY IMPORTANT( CHECK THE PICTURE)

Question 4

Coaxial

Answer 4

▪ 100 Mbps, 500 meters

Question 5

Coaxial Twinaxial

Answer 5

▪ 10 Gbps, 5 meters
▪ 100 Gbps, 7 meters
MORE PICTURES

Question 6

Tip:

Answer 6

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

Question 7

Plenum Cable

Answer 7

▪ Used when running cables horizontally in a building across a particular
level

Question 8

Riser Cable

Answer 8

▪ 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

Question 9

Rollover/Console Cable

Answer 9

o A type of null-modem cable that is used to connect a

computer terminal to a router’s console port

Question 10

Crossover Cable

Answer 10

o Connects two Ethernet network devices directly, such as

two computers without a switch or a router in between

Question 11

Power Over Ethernet (or PoE)

Answer 11

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

Question 12

Snips or Cutters

Answer 12

▪ 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

Question 13

Cable strippers

Answer 13

▪ Strips the end of the cable to prepare it the attachment of a RJ-45 or
other type of connector

Question 14

Cable Crimper

Answer 14

▪ 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

Question 15

Cable Tester

Answer 15

▪ 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

Question 16

Multi-tester

Answer 16

▪ 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

Question 17

Wire Map tool

Answer 17

▪ Like a cable tester, but it works specifically for twisted pair ethernet
cables
▪ It can diagnose any issues with that cable

Question 18

Open Pair

Answer 18

o Occurs when one or more of the conductors in the pair are

not connected to a pin at one or the other end

Question 19

Short Pair

Answer 19

o Occurs when the conductors of a wire pair are connected

to each other at any location in the cable

Question 20

Short Between Pairs

Answer 20

o Occurs when the conductors of two wires in different pairs

are connected at any location in the cable

Question 21

Reversed Pair

Answer 21

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

Question 22

Crossed Pairs

Answer 22

o Occur when both wires of one color pair are connected to

the pins of a different color pair at the opposite end

Question 23

Split Pairs

Answer 23

o Occur when the wire from one pair is split away from the

other and crosses over a wire in an adjacent pair

Question 24

Cable Certifier

Answer 24

▪ Used with an existing cable to determine its Category or data throughput

Question 25

Multimeter

Answer 25

▪ 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

Question 26

Multimeter

Answer 26

▪ 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

Question 27

Punch-Down Tool

Answer 27

▪ 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

Question 28

Toner Generator/Probe

Answer 28

▪ 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

Question 29

Loopback Adapter

Answer 29

``` ▪ 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 ```

Question 30

Time-domain Reflectometer (TDR)

Answer 30

▪ 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

Question 31

Fiber Light Meter

Answer 31

▪ A device that provides a continuous wave of stable source of energy for attenuation measurements

Question 32

Fusion Splicer

Answer 32

▪ A machine that is used to permanently join two fibers together

Question 33

Tap

Answer 33

▪ 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)

Question 34

Attenuation

Answer 34

▪ 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

Question 35

Interference

Answer 35

▪ 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

Question 36

Decibel (dB) Loss

Answer 36

``` ▪ Measures the amount of signal deterioration we are experiencing on a given connection ● Copper o decrease in voltage ● Fiber o amount of lost light ```

Question 37

Copper Cable Issues

Answer 37

o There are many types of issues that could occur withing your copper cables

Question 38

▪ Incorrect pinouts

Answer 38

● 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

Question 39

Bad port

Answer 39

● 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

Question 40

Open

Answer 40

● There is nothing on the other end of the connection or there’s a break in the wires between the source and the destination

Question 41

Short

Answer 41

● Indicates there are two wires are connected together somewhere in the connection

Question 42

Transceiver

Answer 42

▪ 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

Question 43

Dry Cleaning

Answer 43

▪ Using light pressure while rubbing the end face of a fiber cable or connector with a dry-cleaning cloth in one direction

Question 44

Wet Cleaning

Answer 44

▪ Moistening a piece of lint-free cloth with a fiber optic cleaning solution and wiping the end face of the cable or connector

Question 45

Duplex Mismatch

Answer 45

▪ 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