Straight wired and crosswired Ethernet connection?

[HappyHippyDad]

Evening everyone..

I have just been experimenting with a cat5 wall plate on one end of the cat5 cable and an RJ45 on the other end.

The RJ45 connects to my router and the wallplate is situated in the office. I then connect a standard Ethernet cable (RJ45 on both ends) from the wall plate to the computer.

First of all I wired my cat5 cable as 'straight wired', ie both ends as T568A, it worked fine. I then thought I'd try it 'crosswired' and changed the wall plate to T568B keeping the RJ45 as T568A, it still worked. Why do they both work? Does it matter which way you wire it if they both work?

Cheers.

 

[rolyberkin]

As long it is wired the same way at both ends they will work as a network cable, the issue comes when they are used to connect computer to computer rather than computer to network.

 

[Lucien Nunes]

Most modern devices are auto-uplink, i.e. they detect which pair is which when they see the far end, and adjust themselves to suit. That way, either type of cable will work with any pair of devices.

This was not always the case - older devices did not have the capability to swich pairs so the correct cable was necessary according to what was being connected.

 

[Richard Burns]

Does data transfer not use all cores of the cable?
If data just uses the cores with blue and brown then there is no change.

 

[Lucien Nunes]

100BASE-T uses orange and green pairs only, being the ones that are crossed in a crossover cable. As HHD states this is equivalent to TIA 568A at one end and B at the other. 1000BASE-T uses all four pairs, but all 1000BASE-T hardware is auto-uplink equipped.