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Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Jay Bollyn
Honored Contributor

Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?


Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

We are running new gigabit switches with a mix of 100Mbps and 1000Mbps devices. We are seeing what appears to be intermittent network connectivity problems in one user area. There is a old Cat5e cable there which is coiled up and cable tied because it is too long. That device happens to be gigabit. Is it likely that EMI/RFI interference is causing this problem?

My understanding is, the greater speed of gigabit can be a problem if the Cat5e cabling is old or coiled up excessively. The coil is taking up about 10' of the cable.

TIA - J.
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22 REPLIES
Roger Faucher
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Jay:

I would probably uncoil and re-test. 10' of cable should be pretty easy to find a temporary home for (up and down a wall?).

Make a great day buddy!

Roger
Make a great day!

Roger
Hugo Tigre
Trusted Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Hi jay,

you should test that cable off course, but i doubt the cable is causing problems on the other computers or links, and from what you said you have an area (assuming several links) with the same problem.

The first thing you should check is to see if there aren't any broadcasting storms happening . You should have all switches with a Spanning Tree Protocol active.

regards,
hugo
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Hi Roger,

That area has a networked printer and a PC plugged into a little Netgear unmanaged gigabit switch. The switch is plugged into the wall socket. The wall socket is connected through the drop ceiling cat5e to the new managed gigabit switch in the network closet. (The cable in the ceiling is not going to be replaced.) The PC is a special use secured PC. All it does is act as a print job release station for our print management system. Every once in awhile it will display 'system down'. Rebooting the PC brings it back to normal functioning.

I have replaced those cat5e cables with new cat6 cables, not coiled up at all. I read an article recently which listed lots of good reasons to use cat6 cables instead of cat5e. I will need to keep an eye on it, because the problem is intermittent, and the users in that area don't always notify me when there is a problem.

We are in the process of replacing all cat5e cables with cat6 anyway. The old cables are just being thrown out.

Hi Hugo,

All that is attached is the one PC and a networked printer. When the PC goes down, the printer is also unavailable, because all print jobs flow through the PC to the printer.

We are only days from closing until Jan, so I think I will just keep an eye on it until then.

The 'system down' msg is generated by the print mgmt app, so I don't really know exactly what it means. The guy who administers the print mgmt system thinks it is a network connectivity issue of some kind, but I think that is just his hunch rather than a certainty.

J.

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Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

The 'system currently down' just happened again. At that time, I could ping the printer successfully from a different PC on the network. I then pinged the PC from a different PC on the network, and it was unreachable. So I need to figure out why this PC is falling off the network.

I'll check the winXP Event Log tomorrow. Perhaps that will have a hint.

J.
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Jules
Esteemed Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Can ping printer but not computer - cable is OK. Problem is computer. Try replacing the ethernet PCI card (or if ethernet is onboard, try a PCI card.
---++++Only read the manual as a last resort++++---.
Jules
Esteemed Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Could also try a different port on the Netgear switch.
---++++Only read the manual as a last resort++++---.
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Hi Jules,

I agree, this is some problem with this particular PC. We have recently replaced the RAM in this PC because it was also giving intermittent STOP - PARITY CHECK errors. I thing this is eventually going to be a motherboard Dell warranty swap (the NIC is integrated). I don't think this PC has any expansion slots at all (for a test add-in NIC), because it is a 'small form factor' Dell model. SFF PCs are fine until there is some problem with the PC, or until you want to add something in; then you are screwed.

We are not getting parity check errors since the RAM swap, but I think that is a separate issue from this intermittent network connectivity problem.

J.
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Roger Faucher
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Hi Jay:

The Event Viewer is a good place to start (as you said). Swap out the switch (and its power brick) if another is available. Please post the Dell PC model and whether the memory was swapped with an identical system or not.

Make a great day!

Roger
Make a great day!

Roger
Jules
Esteemed Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Yep - can't do much if no PCI expansion slots. Bummer!
---++++Only read the manual as a last resort++++---.
Roger Faucher
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Jay:

Actually, you could try a USB to Ethernet adapter. I keep one for just such occasions.

Ciao!

Roger
Make a great day!

Roger
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Nothing unusual appears in the Event Log, so I think a hardware problem is unlikely. And I believe network connectivity problems do not tend to be logged there. Device Mgr does not indicate a device problem.

I have removed the little switch, since it is not needed anymore anyway. Each device (printer and RS) is now plugged into its own socket on the wall.

So if the problem persists, I am going to plug the printer in where the RS is currently plugged in, and vice versa.

This is a Dell OptiPlex SX280. The RAM modules were swapped under Dell warranty, so I think that was done correctly.

If this happens again, I need to see if it has a valid IP addr from our bootp server.

This has been happening ~ since the switch in the closet was upgraded from 100Mbps to 1000Mbps, so I tend to think something about the switch is causing it. We have plenty of PCs plugged into that switch, without a problem. And we have a Ghosted RS on another floor, with its own 1000Mbps switch, which is OK. I think all the switch ports are autosense full duplex. I don't have direct control of the switch port configuration.

I hope the wall socket swap takes care of this, because I am running out of good ideas.

J.
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Hugo Tigre
Trusted Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

I think you should try what Roger Faucher said, at least it will eliminated the change that could be a NIC problem.

One other thing, that computer could be losing it's connection because a ip conflict with another machine.

Sometimes when you have WINS in your network, these kind of problems happen. Even if you are not seeing any error messages in the log files, you should check the DHCP/BOOTP Server and WINS Server (if any) to check this.

good luck,
hugo
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

I don't have a USB/NIC adapter.

I think, if there were 2 devices with the same IP addr, it would not help to reboot. But reboot does clear the problem.

We have WINS disabled on our network.

I don't have direct access to the bootp server. If it fails again, I need to see if it has a valid private IP addr at that time, yet cannot be pinged for some reason. Or if it does not have an IP addr at all, at that time.

I am hoping that removing the Netgear switch, and changing the closet switch port, will clear this up.

J.

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Jules
Esteemed Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Surely it wouldbe worthwhie buying a USB to ethernet device, and trying it, just to eliminate this posibility
---++++Only read the manual as a last resort++++---.
Hugo Tigre
Trusted Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Jay,

Actually in the case i described (the on where it was WINS fault) a reboot will fix the problem momentarily.

And even if you don't have WINS the same might happen, because when the two or more computers that have the conflict detect this problem, they "shutdown" their network link, and if you reboot one of the machines, for example, that machine will have temporarily network connection, and can last several minutes with network connection.

Also don't forget that if there is a conflict it can come from any network device, like a printer for example.

regards and good luck,
hugo
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Thanks all -

I will reply here when this is resolved.

Leaving the thread open for now.

J.
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John Collier
Esteemed Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Jay,

Just found your thread. I know it seems as if you have left this issue for now, but I thought I would take a minute to add some more food for thought.

Being a network-type-person, I have seen many different issues similar to yours and even had one or two of my own, so I hope my previous hemorrhoids will serve to assist you in relieving your own.

It was mentioned above to look for broadcast storms. While it is possible, it is not exactly likely if this is the only device that shows the symptoms you describe. The best way to have network storms worked out as a possibility is to have the network admins or the network opps folks check through the NNM system for indications of such problems. If there is no NNM system in place, then you will have to hope that they have detailed logging turned on for each of the switches and routers with a large enough buffer to be of some service. If no NNM exists, call them AS SOON AS the issue appears so that they can scour the logs while they are fresh.

The hardware is a definite possibility. I fought that battle at home for quite some time with my wife's old PC. I could find nothing in the logs to point to a problem, but I couldn't do any data transfers of any size at all without timeouts and really sporadic behavior. I seem to recall that one driving me to drink and then forcing me sober again before i finally bit the bullet and replaced the NIC. Of course, by then I had replaced virtually everything else so it was really the only choice left...

Since you have replaced the cables in question, I would think that you are most likely safe there. The only weak place I see in your description is the wall jacks. You did not indicate how new/old they are. If they were around in the Cat5e network and have not been adjusted since, they would be suspect is all else fails.

The one other thing that I have not seen mentioned but jumped right out to me based on experience on the job is the network configuration in reference to the switch/client connection.

On more occasions than I could possibly count (or would ever want to anyway) we have had issues where auto-negotiation has virtually killed network traffic between devices. The nasty part is that there will be little to no indication of it in the logs of a PC and, once again, unless the switch is configured to log such things you will see little to no indication of it there either.

My last suggestion to you would be to go into both the switch and the PC and hard configure the link speed between them. Try it first at full speed, then back off to a lower one if the issues still exist. It will help to diagnose any hardware or cable failures if you still have any doubts in that area as well.

What I fully expect is that you will see the issues completely disappear with a hard line speed config between the switch and PC or you will find a faulty NIC card in the PC.

Happy Holidays to you all!
"I expect to pass through this world but once. Any good, therefore, that I can do, or any kindness that I can show to any human being, let me do it now. Let me not defer or neglect it, for I shall not pass this way again." Stephen Krebbet, 1793-1855
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Hi John,

Thanks for the detailed reply. The problem has not come back, but we closed for the semester 20-Dec, and did not use the printers much during the preceding exam period, so it is hard to tell. I won't have anything new to report until mid Jan.

Happy Holidays to all!

J.
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Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

We are still getting memory parity errors, even with the replacement RAM. So the motherboard (with integrated NIC) has been replaced under Dell warranty.

I will keep an eye on it for a couple days, and report back here.

J.
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Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

The printer has been somewhat busy for one week, and there have not been any problems that I know of. Looks like the replacement motherboard/integrated NIC was the solution.

I will need to watch it for another week to be reasonably sure.

J.
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Jules
Esteemed Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

Hi Jay - Glad you now have a NIC that is working.
---++++Only read the manual as a last resort++++---.
Jay Bollyn
Honored Contributor

Re: Intermittent Network Connectivity Problem Cat5e/Cat6 - EMI/RFI Interference?

seems OK so far

J.
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