Re: [nsp] Questions:

From: Stephen Sprunk (ssprunk@cisco.com)
Date: Thu Jun 13 2002 - 15:01:30 EDT


Thus spake "Jeronimo Diez de Sollano Velazco Aceves" <jdiez@bestel.com.mx>
> I have an ATM link between two routers connected bact to back with a PVC.
> The link utilization is below 40 % but i get intermitent discards in the
> show interface output. If i send a ping no packet seems to be lost, but i
> still concerned about those drops. I´m trying to look if is because some
> internal process of the ATM interfaces. This because if i change the
> interfaces to Serials in the same cable and same routers i don´t get any
> drops.

Are these output or input drops? If they're input, you have buffer problems.
If they're output, you're getting some periodic congestion and they're probably
normal.

> Other concern i have is about the buffers, i´m getting 85 failures in middle
> buffers, i tryed the cisco Output interpreter and it says a lot of thingas
> about large buffers and things, but nothing about those 85 failures that i
> get in the show buffers output. My router has a lot of free memory and the
> max buffers allowed is 1600 vs the 689 free of 750.

85 failures out of how many hits? If it's less than 1%, you don't have a
problem.

> does anybody has a document about real buffer tunning. All that
> i can get from the cisco page is a simple document that says that to
> change the buffer settings you need to be an expert, but no
> documentation to become an expert.

If I were going to release such a document to the public, the first 99 pages
would say "don't change anything", and there'd be one page describing how to
tune. Spend your time learning something more useful.

S



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