Question We have a small Pier to Pier network setup with 13 systems and one printer  connected to 2 eight port hubs. We are having all kinds of instability with the  network. A station might see all the other stations on the network but they can't  see him or visa-versa. Sometimes it will appear and other times not.  When we made the cables for the stations, we used cat 5 cable (4prs) with the  following wiring:  Pin 1 wht/org, Pin 2 org/wht, Pin 3 wht/grn, Pin 4 grn/wht, Pin 5 wht/blu, Pin 6  blu/wht, Pin 7 wht/brn, Pin 8 brn/wht.  We tested them using a TBase cable tester, and they passed just fine. Looking at  your diagram for correct wiring, it looks like you have some colored wires in  different locations, but it is still pin for pin. Is there a reason why ours would be causing our problems? Answer  Regarding your question on RJ45 pinouts, I would say that you are probably experiencing crosstalk  problems. The reason is this, Ethernet uses pins 1 & 2 and 3 & 6 on 10/100BaseT networks (I know it's a funny  way to do it but thats how it is!). One pair is used for transmit and the other pair for receive, so pins 1 &  2 at one end will connect to pins 3 & 6 on the other end and vice versa. In the correct wiring  configuration each signal path (transmit or receive) is on its own twisted pair of wires, the twists help to  eliminate crosstalk. With your wiring, pins 3 & 6 are  split between the green and blue pairs making them  susceptible to crosstalk (or noise), this also gets  worse when using higher speeds (100BaseT or  Gigabit Ethernet). The reason your tester didn't pick it up is because it  only tests for continuity, shorts, crossed pairs etc.  (not split pairs) you would have to use a scanner  (like the Fluke DSP or MicroTest scanner) to find a  split pair.
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Cabling problems? - Split Pair