Skip to main content

Module 1.1: Ethernet cables

  • If you want to learn about driving, you first have to understand what a road is.
  • In this case, network "roads" are cables, but can also be fiber optics or wireless networks
  • We need to understand how to create one of these "roads" from scratch
  • We will be using either category 5 "cat5" or category 6 "cat6" cables
  • cat5 has a max speed of 1 gb/s, especially if it is labeled cat5e, or cat5 extended
  • cat6 has a max speed of 10 gb/s
  • The cable ends for these are not interchangeable, as one wire is a bit thinner than the other (cat5 is 24AWG while cat6 is 23AWG, a bit thicker)
  • The ends are called RJ45 and has 8 slots
  • When viewed with the flat side towards you, these are the colors:

Download O O G BI BI G Br Br.tiff (image/tiff, 429.6 KB)


  • This is NOT random
  • The first two orange pairs (1 and 2) are for data transmit
  • The green pairs (3 and 6) are for data receive
  • The blue pair is for power over ethernet (POE) plus (+)
  • The brown pair is for POE negative (-)
  • This color is different from 8 conductor (4 pair) telephone cables which may look exactly alike
  • Reason? Phone cables start with 4-5 as line one, then 3-6 as line two, 2-7 as line three and 1-8 as line four
  • Each of these has up to 90 volts on each pair (when a telephone rings) so we separate our color code for computers
  • Reason? Plugging a computer into a phone outlet will not burn out the network card on the computer this way

Migrated from Apple Server Wiki. Original page ID: V6c8B7u