Lesson 4: Troubleshooting Ethernet Networks

Question 1

Define the Top-to-Bottom/Bottom-to-Top OSI Model Approach

Answer 1

Validating network components by testing at each layer of the OSI model in sequence of top to bottom or bottom to top

Question 2

Define the Divide and Conquer Approach

Answer 2

Using the OSI model, in this approach one would start with the layer most likely to be causing the problem and then working down or up depending on what the tests reveal

Question 3

Define a channel link

Answer 3

The entire cable path; Network transceiver (end system), patch cable between host and wall port, structured cable between wall port and patch panel, patch cable between patch panel port and switch port, and another network transceiver in the switch port

Question 4

What is the first step when investigating link failure?

Answer 4

Check that the patch cords are properly terminated and are connected to the network ports; check for kinks in the cable

Question 5

What is a loopback tool used for?

Answer 5

To test ports at the host or switch to determine if there is a bad transceiver

Question 6

When troubleshooting a permanent link, what are things to look for?

Answer 6

Check to verify the cable type is appropriate, could need a higher Ethernet standard, or whether or not shielded is needed, or plenum rated cables for plenums spaces

Question 7

What is a time domain reflectometer?

Answer 7

Used to measure the length of a cable, and other cable imperfections by transmitting a short signal pulse down the cable.

Question 8

Define a multimeter/wire map

Answer 8

A tool used to identify terminations/pinouts of cable and can detect open/short circuits, incorrect pin-out/termination/mismatched standards

Question 9

What measurement is used to describe attenuation of a cable?

Answer 9

Decibel loss (dB) measures loss of signal strength, the higher the dB, the greater the signal loss