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Very high number of buffer failures

amlendu_kumar
Level 1
Level 1

All

the show buffers pasted as following

Buffer elements:

491 in free list (500 max allowed)

18929063 hits, 0 misses, 0 created

Public buffer pools:

Small buffers, 104 bytes (total 1000, permanent 1000, peak 3970 @ 1w2d):

995 in free list (250 min, 1375 max allowed)

35499283 hits, 4324890 misses, 71508 trims, 71508 created

1927801 failures (0 no memory)

Middle buffers, 600 bytes (total 25, permanent 25, peak 2146 @ 1w1d):

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

11249741 hits, 5323403 misses, 34260 trims, 34260 created

4237365 failures (0 no memory)

Big buffers, 1536 bytes (total 50, permanent 50, peak 1225 @ 1w1d):

50 in free list (5 min, 150 max allowed)

1374918 hits, 3759526 misses, 15144 trims, 15144 created

3018838 failures (0 no memory)

VeryBig buffers, 4520 bytes (total 10, permanent 10, peak 278 @ 1w1d):

10 in free list (0 min, 100 max allowed)

474945 hits, 2543899 misses, 2362 trims, 2362 created

2543899 failures (0 no memory)

Large buffers, 5024 bytes (total 0, permanent 0, peak 188 @ 22:20:27):

0 in free list (0 min, 10 max allowed)

There is a high number of buffer failures even though there is enough memory and CPU resourses. The total packet drops is very low so this does not produce any negative impact elswhere.

What could be the reason/s

TIA

5 Replies 5

m.lammerse
Level 1
Level 1

Hi Amlendu,

when a packet arrives on a router interface, it is classified as small, middle, big, very big or large and put in the appropriate ring buffer.

It might happen that there is no space at that particular time (a miss) or that there is space (a hit). A miss leads to a dynamic allocation of the required buffer space.

A failure, however, indicates that there was no memory available and that the packet was lost.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/fun_r/cfr_1g07.htm#wp1057860

If the number of failures does not add up to the total number of drops on the interface, this may be a cosmetic bug.

HTH

Marcel

Hi Marcel

memory can be ruled out as show mem sum produces the following

SCB_NBO1R_57725>sh mem sum

Head Total(b) Used(b) Free(b) Lowest(b) Largest(b)

Processor 629DD8E0 64104224 8996000 55108224 51721180 53785104

I/O 6700000 26214400 2544888 23669512 14042992 2366927

There is 55 mb for processor and 23 mb available for IO. Is it possible this is a IOS bug ?

This many buffer failures just doesnt make sence.

Hi Amlendu,

cosmetics bugs like these are certainly not uncommon. What ios version are you running?

-Marcel

I have decided to upgrade this router to 3745 from 3640.

Without running the same ios version, I hope? It'd be interesting to see if this solved the problem. Do let us know.

Regards,

Marcel

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