[c-nsp] FE ignored errors

[Rodney Dunn]

> 
> hmm...your output is a bit different...probably because you're running
> 12.0S and I'm running 12.2S.
> 
> here's part of the output looking at a transit interface's input...this
> output interface is a T3 that connects the transit router to part of our
> backbone.
> 
> Serial4/1/0:
>  MEMD txacc 0x1A8A: 4853423 in, 7361306 drops (0 paks, 0/10793/10793 bufs)
> 44210kbps
>    No MEMD acc: 4853423 in
>       Limit drops  : 6339503 normal pak drops, 0 high prec pak drops
>       Buffer drops : 1021803 normal pak drops, 0 high prec pak drops
>    No MEMD buf: 0 in
>       Limit drops  : 0 normal pak drops, 0 high prec pak drops
>       Buffer drops : 0 normal pak drops, 0 high prec pak drops
> 
> This shows a whole bunch of packets got dropped because there were no MEMD
> buffers and the VIP had no more room for RX buffering.

I'm not sure which ingress VIP this rx-buffering output was
for but the bottom line is the more rx-buffering capability
you have the more packets you can hold on the ingress vip
waiting for the outbound interface to transmit.

Bottom line is for that situation you have congestion on the
egress side.

To stop rx buffering turn on QOS for the egress link:
fair-queue for example 

Clear the counters and watch 'sh int | incl drop' and look
for any interfaces seeing output drops.  It's usually
those that you will see rx-buffering happening for on
other vips.

Stop the rx-buffering (just as a troubleshooting step)
and see if your ignores on the ingress stop.


If your problem is ignores during bursty traffic due to
the CPU overloaded doing that doesn't help.

> 
> > We do (1000 in, 500 out), but I'm not sure it made any difference - it's
> > hard to measure, as the effects *are* highly sporadic.
> 
> If you're still seeing occasional bursts of 100k+ ignores, it doesn't
> sound like it's helped much.
> 
> ----------------------------------------------------------------------
>  Jon Lewis                   |  I route
>  Senior Network Engineer     |  therefore you are
>  Atlantic Net                |
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