Overrun frames in Catalyst 6509 interfaces

[luis.gomez-bastarreche]

An etherchannel link between 2 Catalyst 6509 with IOS 12.2(18)SXE5 the interfaces have overrun frames. The connection is done with 4 ports 1G of WS-6548-GE-TX modules installed in every of any 6509. ¿Do you know how can solve these overrun frames?

I`ve attached a file with the config of all interfaces and the sh interface output messages.

Thanks a lot.

[Mark Yeates]

Luis,

You seem to have some very busy ports and possibly some oversubscribion on your line cards. On top of having the overruns I also see flushes on your input queues. I would try increasing the input queue. Here is aguide that should help.

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a0080094791.shtml

HTH,

Mark

[luis.gomez-bastarreche]

Hi Mark,

Thank you very much for your help.

Best Christmas & 2009

[Mark Yeates]

You are most welcome! Did increasing the buffers help?

Mark

[luis.gomez-bastarreche]

Hi Mark,

The link with overruns is part of a group of 6 Catalyst 6509 witch are doing level 2 only. The level 3 for routing inter-vlans and other IP routing is done by an external system.

The document you sent to me refer a by default value of 75, a maximum value of 100 for routing interfaces. ¿Do you know witch can be the maximum value for this input queue for L2 interfaces that are only doing L2?

Thanks a lot again

[Mark Yeates · Accepted solution]

Luis,

I would monitor the interfaces for a few days before adjusting the input queues on the switch. Based on the output from your original post the statistics show that the amount of drops are not that high with the amount of traffic over a two week period. It would be advisable to clear the counters and monitor the amount of drops every few hours and during peak traffic patterns.

I have had to adjust queues a couple of times in the past (and no expert by any means on the subject). After determining that there is a problem with drops I would incrementally increase the queue size on the interfaces while still monitoring the statistics. You should find a number that will significantly reduce the amount of input drops.

Right now your input queues are set at 2000. I would start increasing them by 100 until you are satisfied with the results without jacking them too high. I also don't think it matters whether the ports configured as layer 2 or 3. Here's how to increase the the input queues.

interface giX/X

hold-queue 2000 in

HTH,

Mark

[luis.gomez-bastarreche]

Hi Mark

Next week I'll begin to adjust the input queue as you told me.

Thanks again for your important helpfull and Best Christmas & 2009

Luis