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Help please: Switches don't work, but hubs will

By K.Parker ·
My boss asked me to look at a company he does Telecom work for. Apparently they are having networking issues.

As far as I can tell, the network is set up like this:
DSL line comes into a Linksys router which then goes to a Windows Server 2000 and also a 24 port switch. One of the leads off the 24 port switch goes to the opposite side of the building to another 24 port switch (about 70 - 90 foot run). No one there has much tech knowledge and were unable to give me any further information. They did not even have the logins for the server and router. Apparently they outsource it to another company who, when called about the current issue, said to get someone else to troubleshoot it that they would only work on the server.

Everything worked fine, and no one knows of any changes made to the system. The port that the second switch is on has an uplink button which was activated.

The second part of the office has no connectivity when the second switch is used. If you swap the switch for a hub, then you can get connectivity.

I am baffled. If anyone has any thoughts, comments, suggestions, I would greatly appreciate them.

Thank you so much, in advance.

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Switch

by BFilmFan In reply to Help please: Switches don ...

Is the switch manageable? If so, then someone with access has apparently made a change.

Sounds as if you have an issue in one of the switches, since the wiring itself is functional.

If the swith can't be managed due to a lack of a password, then it would appear the client will have to hack the password or replace the switch.

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Or

by jdclyde In reply to Switch

the switch is bad.

(how did you miss that easy one?)

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Problem fixed

by K.Parker In reply to Switch

I got the problem fixed and kind of feel stupid now. When I got to the site last night, the first thing I did was just swap out the switch with a new one. It didn't work at all, that's when I put in a hub. Have been troubleshooting today and found that one of the NIC cards in one of the computers was faulty. Took that computer off the network and tried the rest of them on a new switch. It worked fine, so I put a new NIC card in the faulty computer and put it back online. It now runs fine also. So everything is up and running. I think it's true that the more people you have looking over your shoulder, the more IQ points that drop. I was so nervous last night that I never thought to check card functions. But at any rate, new card, new switch, everything's now good as new. Thanks for the help though.

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was one port

by jdclyde In reply to Problem fixed

flashing rapidly?

What lead you to this station?

Surprised that the switch wasn't able to handle this. Usually it is a HUB with a bad NIC plugged into it that will take a network down.

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User

by K.Parker In reply to was one port

was *commenting loudly* on the fact that everyone else was getting online but he still couldn't after I put everyone on a hub. I could hear him all the way down in the cabling closet. I tracked down his cable and saw an infrequent/intermittent flashing on the hub for his connection light. I went to his computer and tried to ping the DHCP server, gateway, etc. I got different responses every time. everything from full loss to 3 out of 4 connected. Never did get 100% success on a ping. Tried to ping other computers on his network, same responses. I went to other computers and checked them for connectivity and they were fine. A little slower than usual I was told, but definately better than nothing. So then I pulled his cable and everyone else started getting better cable speed (less collisions from him, I'm guessing). Unplugged the cable from his computer and plugged the other end back into the hub. Plugged a laptop into his wall socket. It worked fine. Took the end of the cable that had been in his computer, plugged it into the laptop, it also worked fine.

Then I put all the other cables into a switch and removed the hub. Everything worked fine. Tried to plug his computer in and all of a sudden people are getting error messages and being disconnected to the server again. Unplugged him, normal operation.

So I took a NIC card from a computer in storage and swapped it out. Reinstalled all the drivers, yada yada yada... Hooked him back into the network and he's running fine. His Outlook kicked on and downloaded 2 days worth of messages, all his network connections logged on.

Stayed around for another 45 minutes and everything ran perfectly. It was pretty weird. I didn't think a faulty NIC card could take down a section of network like that. But once that was changed, everything worked fine. I called them again a bit ago to check and they said everything is still going smoothly.

Sholdn't switches be able to filter out traffic? Like the garbage his card kept throwing out? Or was that what was making a bigger problem as the switch had to work so much to sort out what was real and what was an error?

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Cheap switch?

by jdclyde In reply to User

A decent switch would not forward any traffic that was not to a specific MAC address or the default address of the source system.

Must not be a managed switch, or you could have logged into it and seen the amount of colisions and excessive traffic.

First thing I check after I know the line going TO the switch is good is look for excessively flashing lights. If you don't have network diagnostic tools, it is about all you can do to get a good idea where to start looking.

Cool that you got it going.

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Trend...

by K.Parker In reply to Cheap switch?

I can't really remember the name of the switch they had in there. It was Trend(something), 24 port, 10/100... That's about all I remember. It wasn't working so I just put it to the side and ignored it. They had a 24 port hub and two 24 port switches there that had been replaced as "bad" by other companies. I told them that they might just want to check them and see if it wasn't just that one computer doing things. No use throwing them out if they do still work. Never know when you might need a backup.

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Call manufacture

by jdclyde In reply to Trend...

many hubs and stitches meant for commercial use have long warranties and you may just get a few new ones. I know 3Com is great for this.

It is always worth checking out.

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And...

by K.Parker In reply to was one port

I did try swapping cables in ports to see if it was jsut a bad port. No matter where I put the guy, he affected the whole switch.

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