Packet buffers

Unanswered Question
Nov 10th, 2008

I've Cisco2811. Based on show buffers i decided to increase middle buffers.

By default was 50 and i increased till 100. After it -

Middle buffers, 600 bytes (total 152, permanent 100, peak 152 @ 00:26:04):

102 in free list (10 min, 150 max allowed)

7560920 hits, 2034 misses, 6047 trims, 6099 created

0 failures (0 no memory)

I saw total is 152.

I increased middle buffers to 150 and here is total 191-

Middle buffers, 600 bytes (total 191, permanent 150, peak 202 @ 00:00:40):

153 in free list (10 min, 150 max allowed)

7561423 hits, 2034 misses, 6058 trims, 6099 created

0 failures (0 no memory)

Should i stiil increase buffers or not?

I have this problem too.
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Joseph W. Doherty Mon, 11/10/2008 - 04:02

I see you're concerned about the peak values, but 26 minutes or 40 seconds of stats isn't much to go on, and neither show any failures.

What you might consider is activation of buffer auto tuning, with the "buffers tune automatic" command (assuming your IOS supports it), and see what it does.

rmv72 Mon, 11/10/2008 - 04:33

i did it before manual configuration and it didn't help - i saw same values as before applying automatic

Joseph W. Doherty Mon, 11/10/2008 - 11:29

"it didn't help"

Could be, buffers really didn't adjustment and/or you did leave it run long enough.

Giuseppe Larosa Mon, 11/10/2008 - 05:21

Hello Mike,

I see the same number of misses these counters are not cleared by the change on buffers I think.

Stay with this setting for a week before thinking of another increase

Hope to help

Giuseppe

rmv72 Mon, 11/10/2008 - 05:36

How increasing buffers will influence at router performance?

If i create buffers in advance does it decrease performance?

johnlloyd_13 Mon, 11/10/2008 - 19:51

you should not worry with your middle buffer problem. your output showed that it still has has available count left in its free list, meaning your router's memory can still handle packets that are 600 bytes length. your output also showed that it has 0 count in no memory. it means that there were no failure for allocating memory for this. you should observe first and if you buffer pools has failures on it, then that's the time you should make the tweak.

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