Problem with using 10/100baseT network cable

[lukaka]

10baseT or 100baseT

Hi there, hope you can help me out.

I made a cable for networking, following the T568A norm. I've done this lots of times (i bet everybody once made an utp cable on his/ger own). Anyways, the thing is that once one end of the cable was plugged onto the switch and the other end was plugged on the pc, I had no link at all. (both the switch and the NIC are 10/100 autonegotiation fully capable).

I rechecked the cable, and the pin out was fine. After a while, I downloaded the speed of the interface of my OS to 10mbps, full or half duplex, and then I could get link.

the question: why is that ???

I made an other cable, new cable, new plugs, and I could get link at 100mbps, full duplex. I don't get it.

If anyone can guide me, to find out why did that happend, I'll be thankfull.

regards

lucas

 

[pisoiu]

Re: 10baseT or 100baseT

Sometimes the connectors make poor contacts to the wires due to lack of attention when inserting or due to construction deffects. Some of these defects are not visible. Cut down the connectors and insert new ones, eventually use the other two pairs of wires than previous. Other posibility is the cable, which can be deffective (short-circuit, open wire, sharp bending of the cable, etc.).

/pisoiu

 

[lukaka]

Re: 10baseT or 100baseT

Hey pisoiu,

thanx for your time. The question was just about that. I believe the connectors were well crimped out. I just don't understand why would it work at 10mbps and not 100mbps. I mean, in both cases (10 o 100) , the pins used (according to T568A/B norm) are 1,2,3,6 (white-green,green,w-orange,orange). So, i believe that, if this cable works for 10mbps, then, the cables are correct (not short-circuited, bended, etc, am i rigth?). So, what would be causing that I could transfer data at 10mbps and not at 100mbps ?

thanx again

lucas

 

[Jan Iwaniuk]

Re: 10baseT or 100baseT

For conection switch to PC you must use crossover cable not straight cable.

jj

 

[lukaka]

Re: 10baseT or 100baseT

> For conection switch to PC you must use crossover cable not straight cable.

JJ,

No man, you use the crossover cable for connecting 2 PCs, two routers, a PC and a router. If you want to connect a PC or router to a switch or hub, you need a straigth cable.

lucas

 

[pisoiu]

Re: 10baseT or 100baseT

Higher frequencies data transmissions are sensitive to parasitic capcitances. If a parasitic capacitive load is present in your cable (bending, poor isolation of wires - from factory, etc.) this will affect your data transmission. In your case, the capacity seem to be low enough to allow 10MBps data to flow, but high enough to cut 100MBps transmission. Basically, you have there a low pass filter. Unfortunatelly, such defects can be pointed only with specialised equipment, most of the times are not visible with free eye, since the defect is inside the cable. It would have been really strange a reversed situation...running at 100 and fail at 10.

/pisoiu

 

[sutapanaki]

Re: 10baseT or 100baseT

If you can afford, take the cable that doesn't work at 100mbps, cut it to make it shorter and try again, It may work this time.
BTW, what was the length of your cable when you tried 100mbps?

 

[lukaka]

Re: 10baseT or 100baseT

Hey, thank everyone for the answers ...

I think that pisoiu may be rigth. In some way, my cable may be working as a low passing filter. I don't have any instruments to make a frecuency test rigth now, but, when ever I can, I will.

And sutapanaki, it is just a 5 meter long cable, it is not that long. Just a patch cord. I don't want to cut it yet ... want to make some tests with it first .... thanx anyway

lucas

 

[sutapanaki]

Re: 10baseT or 100baseT

yes, it makes no sense for 5m only. I think this is perhaps short enough to introduce enough cable loss and screw-up your data.