big buffer misses?

pipsadmin · ‎08-22-2008

I have several routers that I manage with Solarwinds Orion NMS, it's reporting Cisco Big buffer misses.

What are these and what cause this error?

branfarm1 · ‎08-23-2008

Hi there,

Basically a buffer is a memory location where packets are stored while they are processed. The device allocates a certain amount of memory for packets of various sizes, and a packet is sent to a buffer based on the packet size. If a packet is sent to the buffer, but that buffer is full, that generates a miss and the packet is then placed in the next higher buffer.

Think of it like having buckets for packets of different sizes, from small to large. If you start getting a lot of packets of one size, and the bucket fills up, you have to move to the next bigger bucket -- you 'missed' the first bucket, and had to go to the next higher up.

There's a good document that talks about buffer misses here: http://www.cisco.com/en/US/products/hw/modules/ps2643/products_tech_note09186a0080093fc5.shtml

Hope that helps!

--Brandon

pipsadmin · ‎08-23-2008

ok thanks, but should I be concerned with this? and is there a way to fix this? so that there are no misses?

branfarm1 · ‎08-23-2008

You will probably only have noticeable problems if the misses are also resulting in a significant number of failures (drops). Use the show buffers command to see if you are having a lot of failures too. If you are seeing failures, you'll need to do some analysis of what could be causing the problem: Why are there so many packets larger than 1524 bytes? Why is the device unable to allocate more memory for buffers? Does the device need more memory? Is traffic coming so fast that I'm losing an unacceptable number of packets in the time it takes to allocate more memory?

I've always operated on the philosophy that Cisco sets default settings to fit 99% of everyone's needs, and that if I feel I'm part of the 1%, I should talk to Cisco first. That being said - you certainly can try to tune the buffers yourself, but I would be *very* careful in doing that, and I wouldn't do it unless I had spoken to Cisco support first.

Good luck!