Packet Loss on Catalyst 2950

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Aug 26th, 2010
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I have a Catalyst 2950 switch that is about three years old now and recently I have noticed poor performance by the switch when I copy or move large amounts of data through the switch, for example I have one server in the switch and another in the next switch, the switches are connected via a Cat5e cable at 100baseTX.

As I copy a 50MB file across I can see when runnning a ping to the other switch every 15 or so pings are dropped with request timed out.  I am looking to find what show commands I should use to see if I can find where the fault lies.  I have used show interfaces so far and I can see high numbers of CRC errors on the switchports that are being used.

Event though the switch is only 10/100 I would not expect it to have any problems copying a 50MB file to another server and certainly not drop packets while doing so.  This switch has had to be added recently from recon hardware due to a layer 3 switch failure and as a result we also have a VLAN mismatch on the switch that is being logged, would a VLAN mismatch severely impact the switch performance or would this just be a notification message from CDP and a bit of a red herring?



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Jayakrishna Mada Thu, 08/26/2010 - 00:54
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The CRC errors that you are seeing are the likely the cause of this issue, can you verify if these are incrementing by huge number during your file transfer. If yes this then its a physical layer issue. Change the cables and see if that fixes the CRC error and the packet drop issue.


kyle.heath Fri, 08/27/2010 - 11:42
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I resolved the problem, it was a duplex mismatch, my servers were set to auto and my switchports to

full.  Once I changed the switchports to auto the CRC errors stopped and I could transfer a 200MB file in 10 seconds again.



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