How many cores are used in a cat5 cable?

[peanut_butter]

Hi,

I have a question regarding cat 5 cables. Are all 8 cores actually used? The routers we use here at work (ZyXEL P660 - not bad routers) come with 4 core cat 5 cables which has got me wondering.

[Caesium]

10Mb and 100Mb use 2 twisted pairs (4 cores), but 1000Mb use all 4 pairs (8 cores). So, it depends.

[peanut_butter]

I see, and is it always the orange & green pairs which are used for 10/100 networks, then the blue & brown if required for a 1GB?

[kidzer]

Yeah.

The actual pinouts that are used (that then determine what color used) are standardised.

TIA/EIA-568-B is the standard used for a straight-through Ethernet cable. If you want a crossover cable you want one end to be the -B pinout and the other to be TIA/EIA-568-A, which swaps pins 1+2 and 3+6, aka Orange + Green.

[peanut_butter]

Hi kidzer, thanks for your reply. Since you bring up the whole cross-over thing I have another question! Are cross-over cables used only when you're connecting directly from 1 computer to another? I used to think it was used when connecting directly to any network device, such as a VoIP phone, but I can connect it either directly from my computer, or through a switch using the same cable.

[Funkstar]

If you are connecting through a switch or a hub, you just need straight through cables, the network device handles the TX and RX lines.

Cross over cables are often needed when you are connecting one non-infrastructure device to another (a PC to a NAS box, a PC to an IP phone for example). However, this has been mitigated some what by most modern ethernet ports supporting automatic MDI/MDI-X.

[peanut_butter]

ok, thanks Funkstar - that makes sense now =) I thought maybe it was pixies.

[oolon]

Most switches and NICs these days are auto switching so you don't need a cross over when connecting switch to switch or computer to computer. They however are handly to have arround as you can alway find on device that seems to need them. Always good to label a crossover though, I have a problem with a "cat5" kvm, the colours were wrong on it. After we have the board replaced did we realise that the problem was infact the use of cross over... strange it worked at all!

[watercooled]

As has been mentioned, cross-over cables are pretty much obsolete with any half-decent networking stuff made in the last decade or so - everything does it automatically if it's needed.