Desktop

Ask something
Discussion Locked

Network connectiion keeps dropping!

0 helpful
7 replies

by techrepublic

Closed to new repliesThis discussion is closed. It stays readable, but it takes no new replies.

Ok, here's one that has me banging my head against a wall.
The players:
1.) The client: A relatively new (< 6 months) Dell Optiplex GX100 with an integrated 3Com 3C920-TX NIC. Running Win98 SE, with the latest 3Com drivers.
2.) The switch: A new3Com EtherFast 10/100 Switch. Has about 10 other users on it, no one else is having problems.
3.) The connection: A short copper run to an Allied Telesyn media converter. Then fiber optic to another converter, and copper to the switch.
The problem:
Starting about 2 weeks ago, the client's network connection would randomly drop. The user stated then that if he rebooted, it almost always came back on. The user also mentioned that it happens up to 10x a day, and that it seemed to happen most often when he left his PC for about 20 minutes or so. He has since backed away from the last statement.
Upon further investigation, I've witnessed the event. When the connection goes down, I could not get it back by rebooting the PC, nor was the PC left alone for any amount of time. The NIC LEDs were off, as were the Link LEDs on the media converters. Now, here's the odd part. I hooked a 3Com hub up on his desk, while everything was showing no link. The hub linked up, as did his NIC to the hub! After removing the hub, we were back to no link. After toying with the media converters a bit, they linked back up. It may have been a coincidence, but toggling the Normal/Link Test button seems to have done the trick.
The Steps taken so far:
1. Replacing the NIC with a new 3Com 3C905C-TX and changing switch ports
2. Adjusting all power management settings to disabled.
3. Hard setting the media converters and NIC to 100 half-duplex
4. Having the fiber optic installer clean and re-terminate the lines
So, does anybody have any ideas? I'm trying to get the fiber installer to replace the media converters, but am really not so sure that that's where the problem lies.....

7 replies

by psyche

It sounds like you have copper issue, if nobody else is having the problem on the same switch, it can be the cat5 cable from the switch to the desktop.

by shanghai sam

Well, at least if it is happening several times a day, you have a chance of finding the problem within a reasonable length of time by successively simplifying the layout. The problem seems to be limited to one circuit, which includes two copper patchcords, two media converters and one fiber cable. All of those are pretty reliable. You didn't indicate how long the fiber run is, which could be helpful. Your FO installer has cleaned and reterminated the fiber line, but has he tested it or run an automated test over several hours?

Has any new cable (or cable replacement) been done in within the last three or four weeks in the area that the fiber passes through? Could it have kinked or nicked that fiber run in the process? Are there spare pairs in the cable that you could try for comparison?

I'd try to bring the computer and the media converter from that end close to the switch and connect the two media converters with a short, direct FO patchcord and see if they continue to operate for a long time. If that works, the problem if probably the fiber run; if it still fails, it is probably one of the media converters that is failing or may not be sensitive enough to work with that NIC.

The final check would be the copper patchcords and the receptacles that they plug into - clean? no bent connections? etc. I recently had a patchcord where the weight of the cord was twisting the plug just enough that the CPU would connect at 100MB but fail to pass data consistently atthat speed. Look for little things that don't look quite right but are not obviously "wrong".

by slyde phaeder

I had a similar problem with a DEll Inspiron 2500 laptop with an Actiontec 82559-based Mini PCI Ethernet Adapter and a Linksys switch, which appears to be an incompatible combination. A quick workaround may be to dedicate a mini-switch to that PC, before the media converter (I used a Hawking PN828ES). You can probably buy some time for coming up with a full fix by slowing that workstation to 10MB Full Duplex in the Advanced Tab of the 3com driver configuration, since it is likely only an issue at 100MB.

by shanghai sam

I had the same configuration with convertors for connections LAN with WAN. First time when I try to use it I had similar problem. A hardware firewall device with 10/100Mb and 100MB convertors can't work fine together but with 10Mb convertors work fine. In my situation was a compatibility device problem, firewall can't receive the MAC address from NIC card.
I think that you must try to use other convertors model or check documentation for a test link switch (leave this ON and see if that solve your problem).

This discussion is closed to new replies.