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Does cable length matter?
Norm Oct-02-01 08:51 PM
I've been banging my head against the wall for a week now! Ok here it is....

I am installing a several computers to a router and am making the cable myself. I am using Cat 5E. I created a cable that was 110 feet and tested it and it did not work. Thinking it might possibly be the RJ45 ends I cut off 6 feet from each end (leaving the RJ45 ends on) and installed tried the 2 new cables and they worked. I have been wiring them straight through. The only conclusion I can come up with is the router can't handle long distances? (these tests have been done with several computers to try and isolate the problem)

I am using a DLink DI-804 router and have received from no help to conflicting answers from DLink.

Please help!


1. RE: Does cable length matter?
lbyard Oct-02-01 09:05 PM
In response to message 0
100 Meters (328 feet) is the maximum length. The cable probably was not made correctly, the wrong kind of cable and/or plugs were used to make it, or it was not installed correctly. How to inspect the plugs is at http://duxcw.com/digest/Howto/network/cable/cable8.htm. The cable and connector requirements are at http://duxcw.com/digest/Howto/network/cable/cable2.htm. Rules for installing the cable are at http://duxcw.com/digest/Howto/network/cable/cable9.htm. Larry

2. RE: Does cable length matter?
Norm Oct-02-01 09:34 PM
In response to message 1
Let me explain how I came to the conclusion that cable length is playing an issue:

I start out with 110 feet of Cat5e cable and a plug on each end. The router and computer show the cable is connected but there is no communication between the two. Thinking it might be the plugs I cut one end off leaving 6 feet of cable with the original plug and cut 6 feet off the other end of the 110 foot cable leaving the original end. I add a new end on each 6 foot cable and both 6 foot cables work. So it is the original wiring job and the original ends on the new shorter cables. When the two 6 foot cables are part of the longer 110 foot cable it doesn't work.

4. RE: Does cable length matter?
lbyard Oct-03-01 01:23 AM
In response to message 2
I doubt very strongly that the router is at fault. The maximum length limitation is not based on signal strength, etc. The length is limited by the signal timing. I have made many cables that length and much longer. The chunk of cable that you removed could be defective. If all three cables were made wrong or with the wrong components, the short ones may still work and the long one not work (see http://duxcw.com/faq/network/ends.htm). The factors are quite complex and we are dealing with a system that is operating at radio frequencies, not DC. Finally, two wrongs could make two rights. Larry

5. RE: Does cable length matter?
Norm Oct-03-01 07:06 AM
In response to message 4
The conclusion!

I was finally given the solution to this problem. I slowed down the speed of the network card to 10 half duplex and it worked. Not sure why but I am just happy it worked.

7. RE: Does cable length matter?
lbyard Oct-03-01 02:59 PM
In response to message 5
A marginal cable, especially a long one, will sometimes work at a lower frequency and not work at 100 MHz. The DI-704 Home DSL/Cable Gateway is a combination router and 4-port Ethernet switch (http://duxcw.com/faq/network/hubsw.htm). It should operate full duplex with a network adapter capable of full duplex operation. Assuming there is no flaw in the auto-negotiation process or the ports, half duplex operation could indicate a marginal cable. During the negotiation between the network adapter and the DI-704, a condition where packet collisions can occur is detected. This condition is most likely derived from corrupted packets or excessive noise (http://duxcw.com/digest/Howto/network/cable/cable4.htm) on the line. The result is that when transmitting the receiver at the port where the transmitter is located is set to listen for packet collisions instead receiving data simultaneously from the transmitter at the other end of the line.

I would not be satisfied with this condition because of the increased probability that there will be network problems (drop-outs, etc.) and data corruption, and the performance certainly will be marginal. The correct course of action is to verify that the cable is made from CAT 5 or 5e cable and plugs, that the cable has solid core wire (for cables longer than 3 Meters or about 10 feet; I have seen longer cables with stranded wireó25 feet--work OK), the plugs are designed for solid core wire, the cable is run correctly (http://duxcw.com/digest/Howto/network/cable/cable9.htm), and the plugs are wired and crimped properly (http://duxcw.com/digest/Howto/network/cable/cable7.htm and http://duxcw.com/digest/Howto/network/cable/cable8.htm). If all of these conditions are meant and the cable and plugs have been carefully inspected, flip a coin, cut the plug off one end of the cable, replace it, inspect it, and test the cable again. RJ-45 plugs are cheap; an unreliable network can be very expensive. Larry

8. RE: Does cable length matter?
stu Oct-10-01 02:18 PM
In response to message 0
Sounds to me like a possible problem with your termination. It's important to make sure that the individual strands are twisted correctly, right up to the point of termination. If this is not done, signal loss and noise may be induced. The 10mps may seems to be working ok but you may well be performing way below this level due to packet loss etc..

9. RE: Does cable length matter?
lbyard Oct-10-01 04:46 PM
In response to message 8
They should not be untwisted more than 1/2" If they are a phenomenon know as near-end crosstalk may cause problems as mentioned. Larry

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