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My network consists of Cisco switches. I am seeing a significant amount (upwards of millions of packets per day) transmit drops between two switches. One being a 3750 and the other a 3560. The peak throughput of this link is only upper 400Mbps, so it shouldn't be a bandwidth issue.

At this point, I am sort of clueless where to look or what tools I can use to determine what packets are dropping and why. I can setup a SPAN port on that link and Wireshark it, but I don't know if that could tell me anything. Does anyone have any suggestions?

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Are you talking about output drops in the show interface output? – resmon6 Apr 5 '12 at 16:04
up vote 2 down vote accepted

How are you determining that your peak throughput is 400Mbps? If it's off the interface counters, especially the 5 minute averages, you could very well be carrying microbursts that are maxing out the interface for very short periods, which don't show up in the counter averages.

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Kyle Brandt wrote a blog about this and why it matters last year. – Ladadadada Apr 5 '12 at 16:32

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