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N5K/2KFEX 10Gb ports High TX pause counts on low bandwidth throughput

James Smith

G'day All,

I am relatively new to the nx family and I presently have an issue of performance issues being reported on a server enclosure that is connected to a couple of 2k FEXs that are connected to a 5596.

The physical connections from the 5k to the 2k show no TX pause hits, but the 2k phyiscal interfaces to the server enclosure show very high counts on the TX pause counters.

It appears to be a pretty simple setup, 2 10Gb interfaces, in a lacp port channel from each module in the enclosure connect to the 2ks. The switch config is pretty standard trunk config.

looking at the physical interfaces on the switch, as I type, the speed is around 13Mbps input and 18Mbps output, so by no mean pushing a 10Gb interface hard. The port channel interfrace is around input 15Mbps and output is 26Mbps, but I see the TX pause counter steadily rising on the po interface and the physical switch interfaces.

The server enclosure has been looked at by the vendor and they are pointing at the high TX pause as a sign of congestion so I am trying to work out what is going from the network side.

Looking at the basics, it look ok to me. But I am clearly missing something as I can't see why there would be TX pause frames being sent out by the N5K when the interfaces look like they are pushing under 1% of the 10Gb capacity.

I've attached the sh int and sh run int of the ports in question, to saving flooding the post with all the config.

Any help would be greatly appreciated. Thanks


Thank You.




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