Anybody could tell the difference between the CAT5 cable and the RJ45 one (crossover based).

RJ45 isn't actually a type of CABLE its the type of connections/ports used by the CAT5 group of cables. there are two different types of CAT5 the straight through and the crossover, im sure someone will post to tell you the difference because i dont know enough to explain that very well.

CAT1/2/3/4/5/5e/6 are cabling standards UTP and STP are the common network cables RJ45 is the network connectors RJ11 is the phone connectors crossover cable vs straight, the difference is the pinout in case of crossover, pins 1,3 are crossed with 4,6. It is mainly used for inter-router, inter-switch connection. But also used to connect two computer together.

why the physical crossover of the wires? can't the programs just realize the data comes from the other pins? then you would only have to have one cable for everything... then again... we wouldn't have to BUY more cables.

When linking two (or more) PC's together you require that the data from one PC goes via its output (o/p) conection/port to the input (i/p) of t'other(s); and visa-versa. Consequently you cannot send data from one i/p to another i/p... Inuts receive data, outputs send data... The signal paths are isolated from each other... When linking just two PCs together you can either use a hub (with standard cables) or a crossover cable - and no hub. A crossover cable is wired so that the input/output conductors are correctly mated so as to allow an o/p signal to arrive at an i/p connection/port. It dispenses with the need for a hub. If you decide to use a hub then all cables ar standard/straight thru style. The hub (in effect) does the cross-over/mating internally for you...; and it cost a little more than a sinmple crossover cable... But as you can only link two PC via a crossover cable the hub allows greater flexibilty (more PCs etc involved) - all with standard cables. But again a hub cost more... Perhaps have read of the basics (and upwards) sections of Jo Helmig's info at: http://www.wown.com It's all there.

Brenton, this is what most new network equipments are doing. The autosensing MDIX ports will deal with both cable schema. Also, some equipment have a II/X switch for the uplink port.

One small error in Response # 2 - pins 1 & 2 are crossed with pins 3 & 6. Pins 4,5,7 and 8 are not used in 10/100 networks.