Why do we need an x-over?
As mentioned previously, an x-over cable is as simple as connecting the TX from one end to the RX of the other and vice versa.
Let's now have a look at the pinouts of a typical x-over CAT5 cable:
As you can see, only 4 pins are needed for a x-over cable. When you buy an x-over cable, you might find that all 8 pins are used, these cables aren't any different from the above, it's just that there are cables running to the unused pins. This won't make any difference in performance, but is just a habit some people follow.
Here are the pinouts for a x-over cable which has all 8 pins connected:
Where else can I use an x-over?
What happens though if you haven't got any uplink ports or they are already used? The X-over cable will allow you to connect them and solve your problem. The diagram below shows a few examples to make it simpler:
As you can see in the above diagram, thanks to the uplink port, there is no need for a x-over cable.
Let's now have a look at how to cope when we don't have an uplink to spare, in which case we must make a x-over cable to connect the two hubs:
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