Ethernet Cable Woes - On and Off every second

Dave

Yes it could be interference. I had a case where a personal cooling fan took the whole LAN down when it was switched on.

On the other hand a piece of cable left unattended especially if it is subject to movement of any kind could well have developed a break during the

10 months.

1 Try shutting down all but absolutely necessary electrical devices.

2 Try substituting the cable. 3 If problem still there substitute the LAN cards in the PC's

Best Paul.

Is this solid or stranded cable? Did you punch it down to a patchpanel/jacks or crimp an end right on?

I'd bet its solid cable with ends crimped on it, which does exactly what you see usually after some ammount of time of the crimps working just loose enough. (punching it down to a jack and running a patchcable is proper).

Otherwise, there could be some interference somewhere, or you might have split the pairs and not wired it per spec?

Most probably it is a autonegotiation issue. Try to set fixed speed/duplex modes on both ends, or try to change one NIC/driver combo.

For properly wired cable, IMO, You'd have to be working right next to welding or high-power radio equipment to even *think* about interference.

How do you know the "once a second" bit?

In comp.dcom.cabling news.motzarella.org wrote in part:

Totally believeable if a cable near the fan had a split pair. Otherwise not.

-- Robert

(snip)

Someone did post here in the past about running ethernet through an arc welding factory.

While I agree that electrical interference doesn't seem likely, there might be some possibility of mechanical effects, such as vibration on a loose contact.

I still have not gotten around to testing 240VAC common mode voltage on UTP ethernet to prove that it actually works. I probably have enough disposable ethernet parts to do it.

-- glen

All RJ45 ethernet connections are electrically isolated to (ISTR)

4,000V via coupling transformers. It's part of the spec.

You should be perfectly safe :-) Let us know how it turns out.

When UTP was new there was a paper published that described the attempts made to induce errors in a UTP Ethernet connection. Copious amounts of cable was wrapped around welders, fluorescent lights, Microwave ovens, and Xerox copiers while BERT tests were run. The error rate was essentially zero.

Over the years, UTP cable has only gotten better in it's ability to reject induced energy.

(I wrote)

Safe, but it will be nice to see that it still works, too. That depends some on getting it only as a common mode voltage, which would be easy with center tapped transformers, but they don't usually use them.

That is what I expect, but sometime I wanted to try it. I think I have a transformer up to 208V, so I might only get that high.

-- glen

Very difficult for it to be interference. Is it Cat 5, stranded, correct wiring (EIA/TIA 568B or 568A)?

Try isolating the problem with a laptop, Fluke, or other Ethernet device. When you go through the cable, do you get the fault, or is it only with the user equipment? If only with user equipment, then that is the problem. Then move the test equipment to the other end of the cable, plug in to the switch or whatever is at the other end using the same patch cables. If you still have a problem, the cable is innocent. Only if the problem only occurs when the cable is in the path, blame the cable.

If the cable is indeed to blame, the chop off BOTH ends, reterminate, and test with a tester. You should probably also test your tester against some known working good cable. Make sure you use the strain relief.

If it still does not work, chop of BOTH ends, and run new cables. You might want to use the old cable as a wire drag, and get it out. Most of the time you just leave the old one in there, but you definitely want to chop off the ends to prevent accidentally using it.

Wrolf

I agree with Al. These cables and associated equipment are usually pretty resilient to interference. I think you should look into simpler issues with the network configuration. There may be couple devices with the same IP address on the same subnet or the equipment is trying to re-negotiate speed or duplex mode or a similar networking related issue and not the cable. Especially considering the regularity of the problem. Interference issues tend to be random except of course when the source of EMI is switched on and off regularly itself.

I still want to know ow the OP determined the "once a second" bit.

....

The blinkenlights on the switch or the network card? However, the OP appears to have lost the thread.