[c-nsp] 7204 VXR, NPE-225, PA-2T3, output queue drops

[Rodney Dunn]

While no always the case most of the time it's bursty
traffic that causes this and you will never see it
in any 'sh int' output.

Here is one thing that I have used to prove if
it's bursting.

put on CAR or a service-policy with policing and
for the conform action and exceed action set it
to transmit.

Then do 'sh interface blah rate' or 'sh policy-map
interface blah' and see if you are seeing any packets
exceed the rate you configure.  Make sure you set the
burst down as low as you can.

The granularity for rate sampling like this is like 25 msec
so you can see burst much easier if that's really what
is happening.

Rodney

 

On Thu, Sep 30, 2004 at 09:27:10AM -0700, Raymond, Steven wrote:
> Got a 7204, NPE225, 12.1(14)E7, a single PA-2T3 with one circuit on it,
> which seemed to recently develop some nasty packet loss.  Checked CPU, it's
> fine at 24%.  Memory OK too.  Physical interface stats show the circuit is
> clean on both sides.
> However the 7204 is accumulating lots of output queue drops on the
> serial1/0.  Running about only 30-35Mb/s (about 10,000pps averaging
> something like 350bytes/packet), which while high, I would not expect to be
> seeing 10s of thousands of output queue drops per minute.  Queuing is
> currently set for FIFO.
> Someone suggested messing with the queuing buffers, which I have never had
> experience with helping at all.  But to my surprise, when he did "hold-queue
> 600 out" on the serial interface config, the output queue drops ceased.
> It seems to be cured now, but it would be the first time for me that such a
> queuing adjustment was necessary.  Any ideas on what exactly is being
> exhausted here?  Is it normal for this bunch of hardware to not even be able
> to handle a DS3?  Is it a software bug or some limitation of this NPE?
> Router is not running any routing protocol, just static and nothing fancy at
> all- just pushing IP packets.  Only two interfaces, the t3 and fe.  My
> experience is mostly with 7500s and I've never seen the problem, so any
> advice or anecdotes are appreciated.
> Thanks
> 
> 
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