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

[Jay Bollyn]

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.

[Roger Faucher]

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

[Hugo Tigre]

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]

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.

[Jay Bollyn]

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.

[Jules]

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.

[Jules]

Could also try a different port on the Netgear switch.

[Jay Bollyn]

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.

[Roger Faucher]

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

[Jules]

Yep - can't do much if no PCI expansion slots. Bummer!