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rakem

network flapping

7 posts in this topic

We have been having problems with out network. Our servers, Switches, Routers, and workstations randomly loose their connections for a short time then will come back up. For example we run a constant ping all day and we will get replies for say 10 minutes, then maybe 10 request time outs, then lots of replies, then maybe 5 time outs.

We have replaced all our switches, and our router and it is still happening. So we think it must be a NIC somewhere causing the problem.

So my question is do you guys know of any tools that let you run diagnostics on NICs over a network connection? We have about 100 computers so to find out exactly which one is causing the problem will be very very hard without the help of some diagnostic software...

Any suggestions would be great, we are getting mobbed in the lunch room! hahah

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What are you pinging as your test point? An inside IP or an external internet IP?

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inside IP's sorry i should have said that this problem is only on a LAN.

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You say that all the components loose connection at some point ? If it was a NIC it would only be one pc, or server. It makes no sence that routers loose connections as well if it is a NIC problem.

You could check for collision on the network, but i have not seen that be a problem for a long time.

If you have Cisco network equipment you can check if Spanning Tree is actrivated, this caused problems for a customer of mine and Clients would loose network access above OSI lvl3 (so no more filesharing/printing but still pingable)

Other than that, i would involve a company that can do measurements on the physical network to check if there is a short or something. It is possible that you need to upgrade the wiring to cat6 (shielded utp) if you are in a heavy industrialized area, or are located close to high voltage powerlines.

I guess if you want NIC diagnostics you can script it with WMI local and have it send the results to a server or something, no idea if something like that exists allready. I doubt you can get the info you want from it though. Last call would be to check for events on servers/clients that show nic failiure, you need to script that too i guess.

Hope it helps a litte,

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Although it doesn't sound like it, if a user is Multicasting on the regular network, it may give you similar issues. Though your time frame for the downtime is short, it may be a computer broadcasting.

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I had an issue once where a crashed PC managed to bring down part of our LAN. I think it was bombarding the network with lots of traffic that was visible on the lights on the network switches. I would disconnect as much as possible from the network and power cycle every bit of kit then plug bits back into the network and watch what is going on.

Snaps.

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