Lost the network???

Here's an interesting one...

My company recently upgraded some network components. We removed a 24-port 10MB Netgear Hub and replaced it with two 16-port 10/100 Linksys Switches. After connecting the systems to the switches, about 95% worked perfectly. The other 5% lost sight of the network. Here's what I know...

The network is a TCP/IP network running all Win9x systems.
The systems that are affected use a CNET Pro120(b) 10/100 NIC. (This same card & driver version are used in other systems that do work) I have connection lights on both the switch and the NIC to the systems that are not working. I cannot browse or ping any system on the network. The systems can ping themselves.

Here's the real confusing part...
If the speed setting is manually set to 10MB Full-duplex, the system works perfectly. It will browse the network and perform all normal functions. If the speed is set to automatic or any other manual setting (100MB half-duplex, etc.) then the system stops seeing the network again.

Any ideas?

Thanks in advance.

Wild Idea: The cabling between the server and workstations may be poor. Try moving one of the malfunctioning workstations into the server room and connect it directly to the switch with a shorter cable. See if it works there.

I can connect the cable, back into the old hub and have it work perfectly, so would this be the case?

I'll try your suggestion though.

With the old hub, were you able to run all the workstations at 100 automatically? I'm thinking the switch is more sensitive to bad wiring for some reason. Call me crazy if you will, but I like to discount the obvious before we decide to "reinstall Windows."

For what it's worth...

I had a simmilar problem with a 3Com 10/100 Hub. If everthing was configured to use 10mb, then everything worked great. If everything was configured to use 100mb or auto, some machines wouldn't work properly. The cause? The circuitryinside the hub was having issues with automatically switching between 10 and 100. I ended up just having to reset the hub (I believe it was power off and then back on again while holding a button) and presto! Everything worked at 100mb.

Mac,
I tried the shorter connection in the server room, but with the same results.

pretzelboy,
I'll try resetting the switch tonight, after the users are off

These switches have no method of resetting, and I just found out that somebody else, cycled the power last night trying to fix the problem. However, the problem still exists.

Well, it turned out to be the NIC itself. I replaced the card with an identical one and it worked perfectly. Not sure exactly how, but why question it. At least until it stops working again. :)

Thanks everybody for your help.

Correction. The system is NOT working again.

The new NIC worked for about 10 minutes, then for no reason, it suddenly lost its connection. It would no longer show or ping anything on the network. :mad:

Any other ideas?

I had a similar situation upgrading from a 10mb hub to a 10/100 switch. I was disappointed with myself at not finding the solution sooner than I did....

The problem ended up being that the cabling was not up to CAT5 spec. It was like Cat 3 or something. So while it sufficed for 10mb connection, it crapped out on the new 100mb network.

So I'd re-check your cabling. Just because it works fine on the hub (at 10mb) doesn't mean it will work on your 100mb switch.

tk

Have you the posibillity to set the not-working-NICs to 10Mbps fixed (instead of auto)? ... and do they work afterwards together with the switch?
If not... connect them (only the wrong ones) to your old HUB and do an UPLINK to the new switch... does it work now?

If you then don't want to recable, perhaps that's a modest solution...

Cabling is all CAT5 that I personally ran in a new building that we just moved into.

I did try setting the cards to straight 10MB and they sometimes work when connected to the switch. If they are set to 10MB full-duplex then they work, if they are set to 10MB half-duplex then they don't. *shrug*

Hmmm so i gather from what your saying that they work indefinetly when set manualkly to 10mb fullduplex? How many systems we talking about here, if its only one or two, is leaving them that way a big deal. Also have you tried changing the net cards for a different type??

There are only one or two systems affected, but one of them happens to be the boss' computer, so leaving them at 10Mb is NOT an option. :D

Another system went down today. Just as I walked in the door, our legal person said her system stopped responding. Same situation. Different brand network card too. Her system ran fine for about 48 hours, only to drop suddenly from the system.

:mad: :mad: :mad: :mad: :mad:

Well, It is starting to look the hub could be bad, I would change the nic speed to 100mps and try running them at half-duplex and see what happens also try auto settings too ;)

Quote:

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Originally posted by Deity:
Another system went down today. Just as I walked in the door, our legal person said her system stopped responding. Same situation. Different brand network card too. Her system ran fine for about 48 hours, only to drop suddenly from the system.

:mad: :mad: :mad: :mad: :mad:

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Yeah its starting to seem like it might be the switch that's at fualt here. Have you tried changing the port in the switch for the problem system. I had a similar broblem a few weeks ago and to fix it a just swapped the computer to a different port on my hub.

Oh yeah, i left this out. Is the problem occuring on only one of the two switches or both?

It sounds like a cabling issue or a bum switch. If you have not done so, invest in a good sniffer or cable tester. There may be slight voltage fluctuations in the cables/connectors. Or you may have a damaged pair which do not show up until you change speeds. A good cable tester will even tell you which pair is faulty and why.

If you are running wall jacks with patch cables connecting them to the punch-downs or hub/switch, the recommended maximum cable length is 295 feet. This was determined a few years ago in preparation for the 100Mbps transfer rate. If you exceed this limit, you run the risk of poor/no response from the line. I think the length limit for standard Cat 5 (from the puter to the wall jack) is 100 feet. I could be wrong on that though.

I would also try swapping another machine that is known good to one of the problem jacks just to make sure that it is not an OS problem or an issue with the network stack.

Are you using UTP (unshielded) or STP (sheilded) CAT5 cable through the walls? If youre only using UTP, u could be getting interference.

I'm pretty sure it's not the cabling or the switches. For testing purposes, I moved one of the problem systems into the server room and connected it with a 5 foot patch cable. It had the same issues. I also tried several different ports on the both switches, with the same results everytime. All the cabling in the office is under 150 ft in length and all a straight connection between the switchs and the systems.

have you tried testing the cabling between the switch and the problem machines by connecting them with a different cable?

Quote:

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Originally posted by tk421:
have you tried testing the cabling between the switch and the problem machines by connecting them with a different cable?

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From the post before, it sounds like he just tried that.
It must be a compatibility problem between the network cards and the switch. Have you tried a different card / working of the same type of card in the problem systems?

Yesterday I tried a new NIC, but it was the same brand...it worked for about 10 mins just fine, then quit with the same symptoms.

I just tried a different brand card, and it seems to work so far, but I guess only time will tell.

Quote:

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Originally posted by BurnFEST:
From the post before, it sounds like he just tried that.

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ahh, you're right. I missed it.

well it looks like you're on the way to getting it. It's either NIC incompatibility, or it's the hub.

Well, it's been three days with the new NICs and they are still running perfectly. *knock on wood* It must have been something about that brand of network card that didn't work well.

Thanks everybody for your help. :)

A little note for this: once-upon-a-time when I began IT-working I was responsible for a PC/UNIX-net... I forced to use NIC's from SMC as they had been common to me - but I found out, that problems on some PC's (slow booting, netware login not available, etc...) disappeared at that moment I used a different type of NIC...

After that I never used SMC's again - even if I beleive that they couldn't be bad... but those we owned had been a pain for a long time (you need time to find out, why things only work sometimes

good luck now... Higg

I'm sure you've done this 100 times, but check the pinning on the rj45 connectors. Make sure they're pinned for 10/100 mbps compatibility. Old cat 5 were just pinned for 10.. Can't remember the exact pinning on the top of my head, been a little while since I crimped a cable. If you have a wire continuity tester, that'd do the job. And.. if that's not it, are there any firmware upgrades on the switches?

That's what I get for reading page 1 and haphazardly responding. Felt kinda silly when I responded and looked.. "oh.. there's a page 2.." damn. Disregard my post.