possible buffers issue causing intermittent connectivity

Unanswered Question
Mar 17th, 2009

I've recently moved a network segment behind a router that seems to be getting hit pretty hard for buffer resources, and there is now an intermittent connectivity issue that's coincided with this move. The connection doesn't go down for long, I've sent 10s of thousands of pings and only drop a dozen or so, but have noticed 3 or more consecutive drops. I'm worried there are too many interfaces in the router and that packets are getting dropped and applications like sql are sensitive enough to these drops that it is visible to end users. My sh buffers output is attached:

It's my understanding that the buffers requirements will pass to the next pool if none are available in the present pool and only when it gets to the last pool, Huge buffers, and there is a failure is the packet actually dropped. Is that the case? If so, the output from this particular time would indicate that there have been no packets drop since Huge buffers show 0 failures, even those all the other buffer pools show failures.

thank you,


I have this problem too.
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Joseph W. Doherty Tue, 03/17/2009 - 19:20

My understanding is the various buffers are for different sized packets. I'm unaware that the router will try next larger size. But whether it does or not, it doesn't seem there are enough buffer failures that should cause a major issue (although some buffer tuning might not hurt - or activation of auto buffer tuning, if supported). So, I wonder whether there might be intermittent interface congestion issues or CPU overload. What's the interface and CPU stat's look like?

WILLIAM STEGMAN Tue, 03/17/2009 - 19:44

It turned out to be an IPS that was inline on the segment leading from the router to firewall that I had overlooked. I removed the IPS from the path and performance is much better now.

thanks for your response


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