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Really Bizarre network issue

By pbtoms ·
I have a computer that cannot see the network. No DHCP, no domain controller. Diagnostics on the 3Com NIC come up "OK". A laptop plugged into the CAT5 cable sees the network. Another computer from someone else's office, plugged in at that desk(same monitor, keyboard, mouse, network cable, etc.) sees the network. The problem computer, plugged into the other office sees the network. I have one computer that cannot see the network at one desk. It finds it at other locations. Other machines at that location can see the network. As an additional twist, when I plug the CAT5 cable coming from the wall jack into a small 5-port hub (in the 'uplink' jack), and then run a cable from the hub to the computer, it sees the network, but slowly! Plugged directly into the wall, it doesn't. The jack in the wall goes to a 24-port hub, into which is plugged the server, and all other workstations.
I'm completely stumped. Why does it need the extra hub to see the network? And why does it see the network when it's plugged in somewhere else? And why do other computers see the network when they are plugged in at the "problem" desk? Aaargh!
We have a small, 10 user network. One server, WinNT 4.0, with a domain. Clients are all 9x. This particular one was 95, upgraded to 98 to see if that might fix it. It has a 3com 93C905BTX NIC. Any ideas? I'm leaning toward the supernatural, myself! :-) Thanks!

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Really Bizarre network issue

by timwalsh In reply to Really Bizarre network is ...

It sound like you have pretty much exhausted the trial and error method of troubleshooting. However, ther is one more thing you don't mention that you might want to try.

Either try the "problem" computer at the "problem" desk with a different patch cord or take the "problem" computer / patch cord combo to a different desk and try them there. I have seen in the past where a given path cord would no longer work with a certain computer (for no known reason). The problem cord would work withother computers and a new cord would work with the problem computer.

If this doesn't fix the problem, I would hazard a guess that you have seriously displeased the IT gods and they have retaliated by visiting upon you a plague of gremlins. You may need to pause for some serious self-reflection to discover how you displeased them and how you can regain their favor.

Good Luck.

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Really Bizarre network issue

by pbtoms In reply to Really Bizarre network is ...

It appears that it was the IT gods at work. I gave up and replaced the computer. The new one works fine, with all of the same cables, etc. The flaky one is also working fine, having been set up to be someone else's computer and moved to a different desk, in the same room. Weirdness abounds in the world.

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Really Bizarre network issue

by des.willcocks In reply to Really Bizarre network is ...

sounds like a physical problem. Some male and female plugs just do not like each other- but will work fine with every other. Try playing with the connection pins. If this one machine works everywhere else then thats it. Why not put it somewhere else? Does it have to be there?

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Really Bizarre network issue

by pbtoms In reply to Really Bizarre network is ...

Poster rated this answer

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Really Bizarre network issue

by OTL In reply to Really Bizarre network is ...

After replacing the jack to nic cable, if it still does not work, problem could be;

1. bad connection in the jack

2. bad connection in server room

3. bad patch cable in server room

4. bad connection/termination on the cable between the server room and jack.

5. RJ48 jack or NIC's connector is dirty/oxidized.

The above could cause the transmit/receive to be below the operating parameters for the NIC on this particular computer, so you would not be able to "SEE" the network.

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Really Bizarre network issue

by OTL In reply to Really Bizarre network is ...

Forgot to include NIC may be going bad, replace it.

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Really Bizarre network issue

by pbtoms In reply to Really Bizarre network is ...

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Really Bizarre network issue

by AKwok In reply to Really Bizarre network is ...

Have you tried plugging the 3com NIC into the other computer and test? It should be the female jack of the LAN card got some bad contact with the suspected RJ45 jack. Try to make a new patch cable or swap the NIC.
GOOD luck! :-)

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Really Bizarre network issue

by pbtoms In reply to Really Bizarre network is ...

Tried multiple cables, and 2 NIC's.

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Really Bizarre network issue

by pbtoms In reply to Really Bizarre network is ...

Oops. Left out some details. I tried two different NIC's (same brand/model, but different cards) and three different patch cables, all with same result. I suppose it is possible that the 3Com 3c905btx NIC in general has a problem, but that seems unlikely. That's the card we use in 75% of the computers in the firm, and have never had a problem.

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