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by spouye

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Hi there,
I have a T1 line and am dropping internet connection very often lately(every 2 days for a few minutes). However every other application on my LAN will be fine, but the internet. The T1 line provider stated that there were 56000 collisons reported on the router. They cannot tell me where it is coming from because it is internally related.
The reason why i believe it, it's because I switched to a regular dsl line hooked up to a basic LINKSYS 4 port-router and this morning it dropped too. And all you do is wait for a few minutes and it'll be back by itself.
So, is it a wiring problem, network card, switch? What is the most efficient way to troubleshoot this? I have about 60 clients and 10 servers. Is there any software that allows to scan and monitor a LAN and would locate collisons?

I really appreciate your contribution

9 replies

by oldefar

Collisions are normal on a LAN. It simply means two devices both tried to transmit and before doing so encountered the other's attempt. Both record a collision and wait to try again.

The reason you see a network down indication is due to the time outs. The slower T1 link (both by bandwidth and by distance) coupled with the collisions gives you an error indication on the nodes.

The real problem is an overloaded LAN. A redesign with segmentation based on traffic flows is indicated. Youmight want to consider dropping any unnecessary chatty protocols as well.

by oldefar

I am sure TechRepublic has some free software in the download section. If not, I can recommend some based on your budget.

by spouye

Thank you very much for the support,
I'd rather go 1st with a free downloadable software. I am a contractor and cannot really have them buy anything. I you could tell me where to find a free version in TechRepublic, i would really appreciate it!

by omie

Just for the process of elimination...for me I strongly believe it is the T1 line or the router configuration, if you don't have problem at LAN computer connetivity.

Another thing to look is on client side are the desktop... "webshots" screensavers and background takes the bandwidth, streaming audio and internet music takes a lot of toll too.

On the server check also the services that is running for somebody was able to intrude into your system.

by spouye

Thank you very much sir for your help and support. I found the problem: there was a trojan in one of the computers. After I isolated it the internet never went down again.
Thanks again!

by oldefar

I did not find a free download on TR site, but here are two free packages that have been recommended in the discussion center.

Ethereal - http://tinyurl.com/7yak
Snort - http://tinyurl.com/7yal

If you can spend a little, I like Etherpeek fromWildpackets. What you are paying for is ease of use and display capabilities.

by spouye

Thank you very much sir for your help and support. I found the problem: there was a trojan in one of the computers. After I isolated it the internet never went down again.
Thanks again!

by oldefar

With 70 nodes (10 servers and 60 workstations) on the LAN, how did you find the device with the trojan and what was that application doing to cause your Internet access to drop for everyone?

by spouye

Well, that was the only user user that complained about not beeing able to get on line. You could only pull up the 1st page of yahoo.com but that's how far you could get. If you try to go further it'll freeze on you. So i ran several virus tools anddetected a trojan. As I mentioned earlier, after isolating that pc for a few days the internet never went down again like it used to up to this day. It's crazy but that's what it was...

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