RJ45 Connectors - Patch Cable for CAT5

This article is 'stolen' from http://www.whcs.com.au/services/rj45.htm

It should be stated that the standard patch cord shown is terminated in accordance with EIA / TIA 568B. However, the recommended terminating scheme used in Australia for new Cat 5 cabling conforms to EIA / TIA 568A where the orange and green pairs are reversed compared to that shown.

In effect, the crossover cable will be terminated to EIA / TIA 568B at one end and EIA / TIA 568A at the other, exactly as shown in the two colour coded plugs as shown below.


REMEMBER To hold the RJ45 connector with the 'clip' on the bottom. To have to the 'opening' (where you insert the cable) facing you.

Straight-Through vs. Cross-Over

In general, the patch cords that you use with your Ethernet connections are “straight-through”, which means that pin 1 of the plug on one end is connected to pin 1 of the plug on the other end. In this particular case it is not then important to wire them as above. Pin 1 is Pin 1 etc etc. However for the sake of uniformity it may be best to wire your cables with the same colour sequence. Cross-Over cables are “crossed” end to end data cables aren't. If you have a network hub that has an uplink port on it then you do not need to make (or purchase a cross-over cable). Just switch the port on the hub to the 'uplink' mode. If your hub does not have an 'uplink' port on it then the only way to cascade another hub or attach a cable modem is to use a cross-over cable. It helps for future reference to mark or attach a tag to the cross-over cable so that you do not attempt to use it as a 'normal' patch lead at some time in the future.

standard.jpg crossover.jpg

REMEMBER To hold the RJ45 connector with the 'clip' on the bottom. To have to the 'opening' (where you insert the cable) facing you.

When to use crossover or normal cable?

Note: NIC = Network Interface Card, HS = Hub/Switch

Use a crossover cable in the following situations:

  • NIC-to-NIC
  • NIC-to-HS uplink port
  • HS uplink-to-HS uplink
  • HS normal-to-HS normal

Use a straight through cable (normal) in the following situations:

  • NIC-to-HS normal port
  • HS uplink-to-HS normal port

Some nicer hubs and switches allow you to choose (via a switch above the port, or possibly through software control) if the uplink port acts like a normal port (like any other on the back of the device) or like an uplink port (RTS/RTR crossed and Send/Recieve crossed).

freesco/howtos/rj45.txt (114925 views) · Last modified: 2005/09/14 00:49 (external edit)
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