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C3750: Packets lost

Dear all,

I hope any of you can help me, or give me an idea where to look ...

I have a stack of 2 C3750-switches (WS-C3750G-24TS-1U) with IPBASE-firmware (12.2(52)SE). 

When I ping to a machine (in this case a virtual one), the replies are always received on the port where the machine is connected, but on the port-channel connecting to the stack of the 'pinging device' the reply comes only for certain initiators, and not for all.


Gi1/0/6: Device/Server I want to connect too ; defined as access port

Gi1/0/25 + Gi2/0/25, as Port-Channel 1: The location of the devices I connect (read as: the uplink to the stack of the PC's), defined for Dot1Q-trunking

Monitoring setup: Source ports: Both: Gi 1/0/6, Po1 (or Po1 replaced by both interfaces)

For the machines which can ping the server I see 2 echo (ping) requests, followed by 2 echo (ping) replies ... So once seen on the Po1, and once seen on the interface Gi1/0/6.

However for other machines, the 2nd reply is missing ; which must be caused by the dropping of these packets in the switch.  At least, I my opinion this must be the reason... But I can't see any (change of) output drops at int Po1, nor at Gi1/0/6.  The CPU doesn't seem to have high usage, and even then, I don't think the error would be constant, as it's always failing for some PC's, and never for others... (at least for a certain time, a few hours it can be constant, the problem dissapears from time to time).

I can't think of any filtering applied in the switch, but of course there must be a reason... I looked through the config a lot of times, searched the internet, but nothing has made me any wiser ...

Can anyone give me some info where I have to look for a solution to this problem? 

PS: I know this is older firmware, but as we don't have a maintenance contract anymore, we can't download newer firmware...And even then, if it wouldn't be a problem related to a firmware-bug, I don't think I would make the upgrade.



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Cisco Employee

C3750: Packets lost

Hello Alain,

I have few questions to understand it better.

- what is speed on Gi1/0/6

- what are the ip addresses of "inging devices" which work and which do not - are they in same subnet

- Do you have ARP/MAC values for "piniging devices" which do not work on 3750 stack

Please also get the following commands:

- show controller eth gi1/0/6

- show controller eth gi1/0/25

- show controller eth gi2/0/25

for same interfaces:

- show queueing int Gix/y/z

- show int gix/y/z switching

- show platform port-asic stats drop interface gigx/y/z

- show ip traffic


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