[c-nsp] OutDiscards (ME3600X)

Nick Hilliard nick at foobar.org
Thu Dec 15 06:26:20 EST 2011


On 15/12/2011 10:06, Christian wrote:
> I'am not sure how I could figure out if there are any microburst. I'am
> seeing those OutDiscards
> on nearly any 100Mb Link configured in this ME3600X network.

It does seem unlikely that microbursts are causing this problem, given the
very low levels of traffic on the port.  I don't find it credible that a
service policy with a buffer depth of 1/2 meg on 100 megs is dropping
packets with a weighted 30 second average load of 35 pps.  That doesn't
make sense.

The most accurate way to detect if there might be microbursts would be to
set up a monitoring session from this port. As the 3600 doesn't support
SPAN yet, you would either need to span from the other side of the link, or
else temporarily insert another switch into the middle and run the
monitoring session from there.

Once you do this, you can then run tcpdump/tshark and save the output to a
.pcap file.  If you then run tcpdump -nr on that file, you can use standard
unix command-line utilities to examine the packet distribution.  If you're
getting huge but very short bursts, then it's possible that you're blowing
the service policy, but as I said, it doesn't look credible given your low
output rate.

At least if you run span/tcpdump, you will have good quality debugging
information to present to Cisco TAC and they may be able to diagnose what
the actual cause of the problem is.


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