Practical Ethernet

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This article is just designed to share some things that I have found out working with ethernet insallations over the years that may be helpful. Of course these tips can't be used where they break cabling regulations, but they work just fine in situations where it's not a consideration, and you just need to make stuff work.

• Ethernet cabling is very tolerent - no matter how sloppy your work is the chances are it will work just fine
  
  
• It really doesn't matter how much of the twisted pairs you un-twist near your connectors
  
  
• You can run gigabit over cat 5 cable just fine and you won't ever notice the difference
  
  
• Gigabit uses all four pairs in the ethernet cable
  
  
• The brown and blue pairs are not used for 100 Mbit ethernet so you can use them to run a second ethernet
  connection, or a telephone
  
  
• You can NOT run 100Mb ethernet up a telephone line (Cat 3) cable hardly at all (this surprised me when I tried it as I thought it would work over say 10 - 15 metres easily !!)
  
  
• When you are learning to crimp RJ45 connectors it's easiest if you only crimp two pairs, omitting the blue and brown pairs
  
• Here's how I remember the order of pins for 100 Mb ethernet. Holding the connector with the pins facing upward and away from yourself (locking tang down) the order is "greenwhite, green, orangewhite, miss two, orange.
  
• Power Over Ethernet (POE) can carry a surprising amount of current utilising the brown and blue pairs on 100 Mbit networks