Wierd Ethernet problem

One network point in an office seems to be failing for no apparent reason.

Its run is about 20m. The port in the office is connected to a patch panel where is is hooked into a managed switch.

When it is plugged in intially it works correctly. Network connectivity, link lights and port on the switch is active.

Every so often the NIC will lose the link and it will not be re-establsed until the cable is removed and reconnected Disconecting it and reconnecting it always seems to fix the problem.

I have traced the cable back with a toner so it is definatly the right one. I suspct a dodgey cable to the patch panel or crosstalk of some description.

Without shelling out for an expensive cable tester is there any software I can use on the computer to narrow down the problem?

paddy

Try a new NIC or different port on the switch.

jjmax

I asked this very same question recently on another forum and the only suggestion was that some NICs support Virtual Cable Tester software by Marvell.
I've looked into it and it's available on some Gigabit cards.
Have you tried replacing the cable from the NIC to the Jack?
Or reinstalling the card drivers or replacing the card?
Might do the trick.

Boro

Are you sure there are no kinks or twists in the cable? The insulation might be gone or a wire might be frayed/broken. Could explain why it might work sometimes and fail others. Best solution (as the others said) is to replace the cable and see if that makes a difference. Oh and change all the ports around, etc, incase its a dodgy port on the switch/patch panel.

Sorry forgot to mention tried a few things.

* Plugged a laptop into the jack as a quick test which worked (not a big surprise).
* The computer/nic in question works fine from another jack in the room.
* Changed the port on the switch that connects it up to the patch in the server room.
* Took out and repunched the cat 5 into the patch panel that runs to that office. (Thats between the switch and the jack in the office)

I havn't tried rewiring the jack yet but it looking more and more like the cable is dodgey.

Its funny when the link goes down, simply uplugging the plug at the switch and reconnecting it brings it back up.

This is one of these problems I hate cause when you think youve fixed it a few days later it happens again!!

Edit: Replacing the cable run back to the server room is not an option I want to think about. Think: Holes in wall

jjmax

Is the connection staying when the laptop is plugged in to it?
Would it be possible to leave the laptop plugged into that point to see if it drops the connection?
On the cable tester thing, there's a company called PPT that rent the things out, they did quote me €500 for a weeks rental of the top of the line Fluke jobby ( that's the minimum ).
I'll PM you their email address.
If you get a tester cheaper elsewhere let me know, cheers.

Havn't left the laptop for any lenght of time cause I need to use it

My next plan is to replace the NIC in the computer with a newer one (the computer is an old p3).

Maybe a newer card will be more tollerent of the problems.

Will report back!

thx for the tester info jjmax and all for the rest of your suggestions

Capt'n Midnight

Try dropping the speed on the link at either the switch or the card whichever is easiest
Instead of Auto try 10Mb Half Duplex to see if that makes it more stable

Also check for powersaving in device manager and control panel - there is a setting to disable the time 2k/XP go looking for DHCP address if the NIC is disconnected for like half a milisecond

If the cable is nearly out of tolerance then some cards might accept it and others won't due to their tolerances.

Swap NIC's with a similar one from another machine in case it's actually the NIC

Capt'n Midnight

Capt'n Midnight wrote:

Also check for powersaving in device manager and control panel - there is a setting to disable the time 2k/XP go looking for DHCP address if the NIC is disconnected for like half a milisecond

This sounds interesting.
I know for a fact this workstation has powersaving turned on. This machine went though a bit of chopping and changing along the way perhaps the NIC in it doesn't like powersaving mode.

Capt'n Midnight

http://support.microsoft.com/kb/q239924/
How to disable Media Sense for TCP/IP in Windows

You may use this feature on a Windows-based computer using Transmission Control Protocol/Internet Protocol (TCP/IP) to detect whether or not your network media is in a "link state". A "link state" is defined as the physical media connecting or inserting itself on the network. For example, assuming a 10bt or 100bt physical media, Ethernet network adapters and hubs typically have a "link" light to indicate the current connection status. This is the same condition in which Windows can detect a link. Whenever Windows detects a "down" state on the media, it removes the bound protocols from that adapter until it is detected as "up" again. - takes about 10 seconds to get a new IP address.

BTW: if it's a laptop make sure it is docked properly - had a one a while back where the NIC would work for about 5 minutes and then stop - the fix was to press the laptop until the dock clicked.

Getting somewhere is seems.

I took apart the jack and cut off an inch of the cable and repunched the connection.
The jack wasn't very well put together in the firstplace it seems.

Put the computer back on this point + did a ping -t and went off for a cuppa.
An hour later it had dropped no packets.
I shall see if it works in the morning

Hobbes

Also check the powersave on the network card. Your machine could be set to switch it off by after a while. Some stuff has a habit of breaking when this happens.