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Webcast-Catalyst9k
New Member

3550 output buffer failures underruns - network is slow

BUFFER ANALYSIS ---------------

ERROR: This router has dropped 16 packet(s) from the 'Small buffers' pool, after   its last reload, due to a physical memory shortage.

ERROR: This router has dropped 16988 packet(s) from the 'Big buffers' pool, after   its last reload, due to a physical memory shortage.

ERROR: This router has dropped 142 packet(s) from the 'VeryBig buffers' pool,   after its last reload, due to a physical memory shortage.

ERROR: This router has dropped 142 packet(s) from the 'Large buffers' pool, after   its last reload, due to a physical memory shortage.

ERROR: This router has dropped 142 packet(s) from the 'Huge buffers' pool, after   its last reload, due to a physical memory shortage.   NOTE: 'No memory' tracks the number of failed attempts to create additional buffers   (and the number of packets dropped subsequently) due to insufficient memory.   TRY THIS: You currently have 8192 kilobytes of shared memory.

ERROR: This router has dropped 74 packet(s) (100%) due to a shortage of 'Huge   buffers'.   NOTE: The term 'Failures' in the huge buffers tracks the number of packets that   were dropped due to unsuccessful attempts to allocate a buffer. This can occur   in spite of (or even because of) the router's attempts to create additional free   buffers when their number declines below minimum. TRY THIS: Use the 'show memory' command to check the amount of free memory.   CAUTION: Care, expertise, and follow-up monitoring are necessary if system buffers   need to be adjusted. Incorrect adjustments can severely affect hardware and network   performance.

Almost all of my connected interfaces are reporting these:

There have been 105286528 'output buffer failures' reported.   If outgoing interface buffers are not available, an output buffer failure is reported.   If an interface buffer is available but the Transmit Queue Limit is reached,   the packet is dropped.

WARNING: 105286528 underruns have been reported, which amounts to 29.25015%   of the total input traffic. This is because, the far-end transmitter runs faster   than the receiver of the near-end router can handle.

Do I need to upgrade my switch?

6 REPLIES
Blue

Re: 3550 output buffer failures underruns - network is slow

Mark:

Has your network environment changed at all since these buffer errors started appearing? Think hard about that. Although this is the first thing to consider in troubleshooting, I have a feeling that it is not related to any change in the network anyway because you are reporting that these output buffer drops are occurring on every user interface.

If no changes have occurred that you think might cause such failures, I would recommend opening a TAC case, peforming a "sh tech" and attaching the output to the ticket.

It sounds like some sort of software failure. Output packets are not placed in output queues, as one might think. The queues just contain pointers that point to the buffer where the offered traffic that needs to be scheduled for forwarding resides.

Taking a guess, some sort of corruption in the IOS may have occurred that is causing this pointer mechanism and the traffic scheduler to fail..

HTH

Victor

New Member

Re: 3550 output buffer failures underruns - network is slow

This is happening intermittently on all my switches cat 4500 and cat 6500's.

Blue

Re: 3550 output buffer failures underruns - network is slow

You should have said that from the get go!

Then the drops must be legitimate...

Are these switches supporting your campus environment with end users?

Give us all the pertinent information..

Cisco Employee

Re: 3550 output buffer failures underruns - network is slow

Buffer failures occur due to overflow of data being buffered in physical memory of routers. ONLY way to free the buffers is to reload the router (which of course implies downtime, so please plan accordingly).

Also, the underruns could be caused by layer 1/2 issues, like bad cabling/patch panels , mismatch of speed/duplex settings on the switch.

Just check the devices connected to ports which see large underruns and make sure they are not operating under half duplex mode.

Please check the points mentioned above, and see if that helps.

Vijaya

Re: 3550 output buffer failures underruns - network is slow

Hi,

Check out the below link on Buffer Missess and Failure hope this will solve your query !!

http://www.cisco.com/en/US/products/hw/modules/ps2643/products_tech_note09186a0080093fc5.shtml

Regards

Ganesh.H

Hall of Fame Super Gold

Re: 3550 output buffer failures underruns - network is slow

IOS bug?
Duplex mismatch error?

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