Network cabling? intermitent conection cant conect to Hub not the cable?

I have three UTP cat 5e cables running from one building to anouther through an underground duct. Cable one is 30m, cable two is 30m and cable 3 is about 70 meters.

head office has a router that runs the network for the site, all three cables are conected to the same router, they run through the duct to the new building and off to three computers around the second building

Cable three works fine  and the computer work happily allows pings and ip allocation via DHCP

Cable one and two will connect for about 2 seconds then drop it for about 15 and try to reconect. some times i get an ip most of the itme i dont. pings fail. The lights on the network cards are sometimes on but mostly off.

I have changed everything, the computers the ports on the router everything except the physical cable and it is the same issue.

I have ran my cable tester on the cables and they all pass so there are no breaks.

Does any one have any ideas, the cables follow the same route up until the point where cable 3 carrys on around the office.

I would assume if some gave me this problem that cable 3 would have the fault due to the length but it is the only one working.

the duct is empty apart from the three cables mentioned.

Thanks in advance.
rama1712Asked:
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Aaron TomoskySD-WAN SimplifiedCommented:
You are perfectly describing bad cable. It can test ok but has way too much signal loss to carry a connection. You can try redoing the ends but here is my suggestion:
Cut all three cables where they arrive at building 2. Put ends on the three going to computers and also on cable 3 going back to the other building. Plug all 4 into a switch.
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ucando1Commented:
If you made the cable, re-terminate the end so the cables. You may have a bad RJ-45.  A cable with 3 of the 4 pairs will give errors like that, make sure the are the same on both sides.

If you have changed all but the cable, the cable is the issue.
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Aaron TomoskySD-WAN SimplifiedCommented:
you can put the working cable 3 into a switch and run 3 lines to the three computers. Ignore the two bad cables
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rama1712Author Commented:
The computer with cable 3 is a long way away from  the other two using a switch is not really possible. the cables all pass the test on my network tester showing all ends are terminared correctly and conected in the right order, shown by the flashing LEDs.
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rama1712Author Commented:
I shall pull a new cable through tomorrow  (testing it first) if that dosn't work i shall go for the hub option. thanks for your help.
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Aaron TomoskySD-WAN SimplifiedCommented:
The only other thing I can think of is after comin out in building 2 the other two problem wires run along power lines or something that is adding noise. You can test this by bringing those two cables back to where they exit and plug them into a laptop or something.
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rama1712Author Commented:
as far as i know they are no were near power but it makes sense to test them before i pull them all the way out, i shall post what i find.

Thanks again, i was getting well anoyed today...
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rama1712Author Commented:
I have recabled, with a now similar problem. i have the pc's and printer now working but have had to drop the conection from Auto @ 10/100mbs to fixed at 10mbs in the network card properties,

At auto the machines say no cable conected at frorced 10mbs they work fine, they are xp sp3 workstations.

My windows 7 laptop auto changes to 10mbs. the thing is the switch is 10/100 and with everyting else works at 100 mbs.
Any ideas why?
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Aaron TomoskySD-WAN SimplifiedCommented:
Signal degradation. There may be power lines in your underground pull or it's a tight fit and the cable gets kinked or streched. Without expensive equipment there is no way to tell. You can try pulling shielded cable or cat6 if it's a problem.
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rama1712Author Commented:
I thought it might be somthing like that. I am still new to cableing, thanks for you help.
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