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Power leaks in ethernet cables

Posted on 2012-03-20
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Last Modified: 2012-04-07
Hello,

We have a simple network (Ethernet Gigabit) for about 100 people, in a 3 levels building. Since a few weeks, we found that some of our cables (RJ45, cat 5e) are not working anymore : when they are plugged into computers, the LEDs on the connector are blinking on / off, and the network is no more found on the computer. On the switch side, the LEDs are absolutely not blinking anymore (for the failing cable).
If I plug a simple switch between my computer and the cable I found that the signal seems stronger and then the connection works.
We are planning to install trunking between the switches on different floors, would it improve that kind of problem ? If not, what could we do ?
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Question by:fcomte
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by:pclinuxguru
ID: 37742742
How long are the runs that don't work?
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by:TazDevil1674
ID: 37742800
1000Base-T is spec'd for Cat5 and Cat5e, but it does push the cable to it's limits. With any above normal amount of ingress noise or substandard equipment you can expect your performance to drop. It's a good idea to use Cat6 with 1000Base-T, but not neccessary.
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by:fcomte
ID: 37742807
Hello pclinuxguru, if by "runs" you mean the lenght of the cables... well it depends, some are long some not, but as this didnt appear on newly connected computers I don't think this is linked (or not in direct link). We changed 2 switches and from that moment the problems appeared.
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by:TazDevil1674
ID: 37742818
Sounds more like the switch isnt auto-sensing if the cable needs to be 'crossed-over' on some ports

If you plug the 'faulty' cables into a working port, does the problem still exist?
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by:fcomte
ID: 37742823
Hello TazDevil1674. It won't be possible to change the cables that easy... any other idea ? Like a "repeter" ?
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by:fcomte
ID: 37742825
> If you plug the 'faulty' cables into a working port, does the problem still exist?

The only way of making work a faulty cable is to plug in in a small switch, just before the computer. As if there was a lack of power...
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by:TazDevil1674
ID: 37742856
You say you changed 2 switches - is one of these the one the 'faulty' cables are connected to?

Are the computers that arent working (because of the 'faulty' cable the same make/model?  Do any others of the same make/model work?  This would rule out auto-switching on the Network Card.

I still think the problem points to config on the ports on the switch (especially if its new)
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by:fcomte
ID: 37742989
Yes the problem partly seems to be linked with the 2 new switches (there is also another connectic problem in our network), but I wanted to know if there are some solutions around putting an appliance like a repeter.
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by:pclinuxguru
ID: 37742997
Well I have short and long runs too... my long runs are 500 meters or so and my short runs are 300 meters or so.

You mentioned signal degradation so first thing in my mind is length. Anything over 300 meters or so can cause it and you would have to put a switch somewhere in the middle.

I have seen old switches handle longer lengths than new ones and vice versa. Just a thought.
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fcomte earned 0 total points
ID: 37743081
> I have seen old switches handle longer lengths than new ones and vice versa.

Hehehe... this is exactly what I'm thinking. This is partly why i want to put trunking on our switches, to see if that will improve the situation.
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by:pwindell
ID: 37772125
300 meter is the MAX length,...and that is when under perfect conditions.    This would have been taught in a simple "Introduction to Networking" in High School.  Whoever ran 500 meter lengths should be taken out an shot.

Trunking doesn't have anything to do with anything in this context.  The physical limitations are the physical limitations,...end of story.

Trunking is running more than one VLAN over the same physical cable,...which is a convenience maneuver,...not a performance maneuver,...it cuts performance in half because you end up running 2 (or more) Broadcast Domains over the same cable which still has the same physical cable limitations on bandwidth.
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by:fcomte
ID: 37772190
@pwindell : thank you for your radical comment. Performances leaks are still occuring. We have a length of max 60 meters, and we are still changing some switches.
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by:pwindell
ID: 37772268
I have experienced that at 30 to 50 meters when the wiring pattern on the cable was not correct because some fool (er,..ok, ok,..so it was me) terminated the ends on the cable incorrectly.  I spent all day doing them wrong,...and all day the next day fixing them.  My fingers were almost bleeding by the time I was done.  I never noticed the problem on the short runs, but when one of the longer ones started to intermittently fail I noticed I had incorrectly followed the wiring pattern.

As far as the Switches,...even cheap $70 switches from Best Buy should work,...it doesn't take anything special just to get the Physical Layer to work.  The more expensive Switches add more functionality and dependability,...but the voltage going out over the wire is still the same,...that is all regulated by industry electrical standards (such as the IEEE standards).
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by:pwindell
ID: 37772503
Also don't allow the cables to lay across florescent lights or the building's heavier power cabling.  It will induce electrical noise into the signal which destroys the signal's data even if the signals voltage may still be fine.

The wiring pattern actually matters on that, because when it is wired correctly the voltage runs over a matched up twisted pair of wires and the twist in the wires generates a magnetic field around the "pair" that blocks out noise (to a point) and allows the signal to survive the elements trying to destroy it.
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by:pwindell
ID: 37772538
You need to follow the T568B pattern,...not the T568A pattern.
Many termination products use color coding and they will show both patterns,...so you have to be sure to follow the correct one.
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by:fcomte
ID: 37794868
Please close question, any answers have been given.
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by:pwindell
ID: 37796796
You have to be the one to close it after you assign the points.
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by:pwindell
ID: 37796806
It would also be good to let everyone know what actually solved the problem or this thread is not useful to keep in the EE Database.
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by:fcomte
ID: 37799631
Problem solved by working with LAG (aggregation) between the switches. The problem seemed also to be one of switch which was turning off / on suddenly, very fast. So yes, the answer was 50% trunking.
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by:fcomte
ID: 37818757
Solution was to work with LAG's between switches.
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