Network Cables ... going mad!

[maccatalan]

Hi.

I noticed that we have two kinds of ethernet (RJ45) network cables :

one for the 10 Mbs
and one for the 10/100 Mbs

I don't understand the differences between both of them since in spite a same color sequence the little cable are always straight.

For example :

let suppose the 10Mbs cable to be :

1: green -- green:1
2: yellow -- yellow:2
3: pink ----- pink:3
4: black ---- black:4

let suppose now the 100 is like :

1: green -- green:1
2: pink ---- pink:2
3: yellow -- yellow:3
4: black ---- black:4

The color order is different but the corresponence is the same : 1<->1 , 2<->2, 3<->3, 4<->4.

Do you know why is there this difference ?

The only reason I see is a magnetic interference but ... I can't believe it.

HELP ME PLEASE! I'M GOING MAD!!!

Thank you,
Pierre.

[ebolag4]

There's no difference. They were just wired differently, but they should work exactly the same.

[maccatalan]

There should be no difference. However when we do test it, we find one. Whenever you don't respect the 100M color sequence then your cable will only work in 10. It has been tested. (I do work in a computer firm and we are used to those problems even if we don't - in this case - understand the why).

then ... does somebody knows the why , please ?

thx,
Pierre

[DeltaMac]

There's probably an engineering ref that would explain a wire color difference, but isn't the only real difference the cat level marked on the cable itself, Are the 10bT cables cat 3 and 100bT cables cat5 or higher. If they are both cat5 or higher, then perhaps the difference is a bad cable (local-manufacture, not to spec)

[Jabberwocky]

10 base-T uses two pairs for data transmission. 100 base-T uses all 4 pairs.

It doesn't really matter which order they are in, so long as they are the same at both ends. Unless you are making a crossover cable, in which case at one end, swap 1-3 and 2-6.

[wiz]

Originally posted by Jabberwocky
10 base-T uses two pairs for data transmission. 100 base-T uses all 4 pairs.

It doesn't really matter which order they are in, so long as they are the same at both ends. Unless you are making a crossover cable, in which case at one end, swap 1-3 and 2-6.

ditto. crossover cables. they usually are used for computer-2-computer networking, not computer-2-lan, right? u get my point?

[rhg]

Originally posted by Jabberwocky
10 base-T uses two pairs for data transmission. 100 base-T uses all 4 pairs.

Sorry, but that's not true. 10baseT and 100baseT use the same two wire pairs 1/2 and 3/6. Gigabit Ethernet (1000baseT) uses all four pairs 1/2, 3/6, 4/5 and 7/8.

The cables have different categories. The cable category suited for 100baseT is CAT5. If you have a CAT3 cable it won't work for 100baseT unless its length is less than 50cm or so. The circuit on your network adapters and hubs/switches do auto-negotiation and this way find out if they can go 100baseT or have to fallback to 10baseT.

[maccatalan]

Thank you RHG for the answer. It seems you know exactly what you are talking about ... but ... what does CAT5 and CAT3 mean (technically) ? what's the difference ? and why have we this very amazing color order solving problem (read the first post of the topic to understand what I am talking about if you did not) ?

Thank you,
Pierre.

------------ Here is a post I was writting to WIZ before RHG answered :

you're right. A cross-cable is used for a computer to computer connection.

however to come back over what jabberwocky said, the order seems to be important since when we don't respect the order, even with good associations (1<->1, 2<->2, 3<->3,...) then the cable works in 10M mode. I can't understand how the cards can detect this. The only reason we see is that when the speed transfert becomes too fast, then inductance interferences appear.

Indeed , the pairs are "melted" (twisted) and then the pairs are alltogether twisted. Maybe they avoid the interferances by making the distance between the wires further by cancelling the pair association by changing the color sequence.

The cards could detect the colors association by sending constant data and checking by error algorithms if they should better use 10 or 100M.

Thank you to tell me if this is the good reason or if there is one other.