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Cable testing
billg Aug-07-01 02:38 AM
I have made some straight thru cat5 cables as in the 'How to' article. Now I would like to test my work, to see if the cables work. I would like some kind of test equipment to help me with this (other than NIC diagnostics). Any suggestions?


Bill Given

1. RE: Cable testing
lbyard Aug-07-01 06:02 AM
In response to message 0
Substitute the cable for another one in an existing network and copy 100 MBytes from computer to computer. It should take about 1 minute and 15 seconds. I copy the cab files in the Windows 98 upgrade (d:\win98\*.*), which are stored on my file server. The adapter diagnostics and c:\>net diag are other available tests. Larry

2. RE: Cable testing
billg Aug-07-01 04:45 PM
In response to message 1
Thanks for your quick response, however, I am starting from the ground up. I don't have an existing network. I am building a home lab. I want to set up a peer to peer 10BaseT system. I have a 3Com 4-port hub. I have three PCs running win2k, winNT and win98SE. I have installed the NICs and run the diagnostics on them. Now I would like to continue to check my hardware by testing the cables that I made. And then go on to the software part. What I would like is some test equipment that would send a signal down each wire and recieve it and let me know if the cable will do the job.


Bill Given

4. RE: Cable testing
lbyard Aug-07-01 07:08 PM
In response to message 2
I'll be happy send you some links if you have an extra $3,000 to $5,000 to spend. Simple continuity testers, which are relatively inexpensive ($30-$50, or probably less at Radio Shack, etc.), send a tone down the line or perform a roundtrip DC resistance test. They do not measure impedance/line capacitance loading or noise at RF frequencies. They are not adequate tests for certifying cables and do not guarantee, by any means, that an Ethernet cable will operate at Ethernet speeds. Your Ethernet adapters automatically perform a better test than continuity testers as they send multiple pulses down the line and Link LEDs on them will not light-up unless the cables are wired so that the correct Ethernet transmitter pins are connected to the correct Ethernet Receiver pins. However, the Link LEDs can be lit and the cable may still not work. Short of expensive test equipment, the best test I know of is to copy and time the 100 Mbytes as I stated. If it sends the 100 Mbytes in a reasonable time, you will have a cable that can send many files in the installed environment without excessive retransmissions caused by corrupted packets. If you donít have a network, then first check the Link LEDS, and then perform the copy test. I have done this many times. My cable tester has been gathering dust. Larry

Q. Why would the Link (or LNK) LEDs be on solid, if there is a faulty cable connecting two Ethernet devices?
A. Solid Link LEDs usually indicate a good network connection between two network adapters connected by a crossover cable or between a PC and hub or switch connected by straight-thru cable, but not always...
10BASET and 100BASE-TX Ethernet interfaces have two transmit pins (+ and -) and two receive pins (+ and -). The rest of the pins are unused. Transmit + pins must be connected to receive + pins, etc.

Solid LINK (or LNK) LEDs on two 10/100 Ethernet devices (network interface card--NIC, hub, switch, etc.) that are connected together indicates that the two transmit pins are connected to the correct receive pins. It does not, however, guarantee that the cable is made properly, is made with the correct cable and connectors, and that will reliably transmit data. For example, the Ethernet standard specifies that the transmit pins be connected to corresponding receive pins with wires from the same twisted pair. It is certainly possible to connect a set of pins using one wire from one pair and another wire from a different pair. The reason it is possible to get solid LINK LEDs and unreliable data transfers is that link determination is made with a link integrity test pulse which is transmitted at a much slower rate than the actual Ethernet signals that transfer data. Broken, disconnected, improperly terminated (coax), or miswired cables are responsible for over 70% of all LAN problems.

5. RE: Cable testing
billg Aug-08-01 01:19 AM
In response to message 4
I'll try it.

Thanks a million

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