Poor network cable quality (TP)

[ATC]

Under normal conditions, straight cables are 1-1 and crossover (uplink) cables are 1-3, 2-6, 3-1, 4-4, 5-5, 6-2, 7-7, 8-8.

Under some conditions however, this is not enough to make the cable carry error-free 100Mbit/s traffic. Very advanced cable scanners may complain about "split pairs", and low-quality switches may be unable to get a link pulse against low-quality network adapters.

[ATC]

Use campus wiring. Under ordinary conditions you would use pair 1/2 for pins 1 and 2, 3/4 for pins 3 and 4 etc. Instead, use pair 3/4 for pins 3 and 6, and 5/6 for pins 5 and 4.

In other words: Swap wire 4 and 6 in both ends.