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Strange network connectivity problems

By adamski ·
BACKGROUN NT - Small Business Server 4.0 SP5, 1 NIC to WAN, 1 NIC to LAN, Proxy Server, Exchange, etc. 15 workstation LAN with NT, Novell, and Ethernet Telephony traffic.

PROBLEM: Beginning last week, after years of smooth running, and with no real regularity, this server loses all connectivity to the LAN. I can?t get to anything that would normally be reached from the LAN NIC; neither IP nor IPX. To temporarily fix this, all I have to do is change the port on the switch that this server is connected to. I can move between the same two ports, back and forth, to remedy the situation when it rears its head, but it doesn?t matter which port I move to, it will always happen again ?eventually. I wrote a ping monitor that just tracksconnectivity to this server and records when a ping is dropped. Most of the time I have no lost packets, sometimes I lose 1 or 2 and then it rights itself, and then sometimes I lose connectivity all together and have to switch the ports. I have noproblems with the Novell Server or Ethernet Telephony connectivity.

ACTIONS TAKEN: I have changed the Ethernet cable. I have changed the NIC involved (now using a 3COM 905C-TX). I have removed and reinstalled all of the Networking components in the server. The switch works fine with every other device on it, so I?ve ruled out that as a problem. The new NIC rules out MAC address conflicts of any kind. The server would complain if there was an IP conflict, but the server produces no Event Log or other error messages at all when this happens. The WAN NIC doesn?t seem to be affected by this problem.

QUESTIONS: Does anyone have any idea what could be going on here, or even how I could find out? Does anyone have a good list of what happens when a new port is used on a switch? What connection information is just refreshed and what is tossed out and then newly reacquired?

Thanks,

David J Adamski

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Strange network connectivity problems

by benjamin In reply to Strange network connectiv ...

Hi David,

1)the 3c-905tx has a know problem with nt sp5, please do yourself a favor and go to 6a 128, Unless you have a good reason..

2)go to the diag soft from 3com and make sure the speed etc is auto, and for the love of god make sure the boot prom is DIABLED.(that's one of the problems).

3) when a new port on the switch is beign use it usually does an arp refresh about 30* per sec. That's it.

4) it sounds to me like you have a mother board problem. (intermitent pci solt failure)/Have you tried changing the slot? if so try testing the card in the wan slot. Also if you haven't already the first thing to try would be un-install all protocols bound to the card.

For more info you can e-mail me at: benjamin@conceptis.com

Good luck and I hope it helps.

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Strange network connectivity problems

by adamski In reply to Strange network connectiv ...

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Strange network connectivity problems

by Barry Hensley In reply to Strange network connectiv ...

David,

Sounds like you've done all the right things. The only suggestion that I have for additional troubleshooting is to reboot the switch when the problem occurs. The only thing that gets buffered on the switch with regard to ports is the arp table. If for some reason, the buffer on the switch is filling up, rebooting it will clear it and force it to refresh.

If rebooting the switch solves the problem, then at least you know that the problem is somewhere in your switch.

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Strange network connectivity problems

by adamski In reply to Strange network connectiv ...

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by adamski In reply to Strange network connectiv ...

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