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Cisco Bug: CSCtd32306 - Bridge traffic perforamce drop after mac aging and learning

Last Modified

Jan 12, 2017

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

3.9.0.BASE 3.9.1.BASE

Description (partial)

Symptom:
On the ASR9000 series "Trident" NP based linecards, a small number
of frames are lost periodically when running very high traffic rates
using very small packet sizes.

Conditions:
This defect is visible only when the following conditions are met:
 - high bandwidth interfaces (i.e. 10G and up)
 - very high packet/second rates
 - very small packet sizes
 - very few destination MAC addresses (i.e. <10)

Background:
As part of the normal MAC table maintenance, the system attempts to
refresh the L3 forwarding table halfway through the MAC aging timer. 
If ALL of the conditions above are in play, we can observe a small number
of frames dropped while these entries are being refreshed.

Note that this implementation is optimzed around the actual network cases
(lots of MAC addresses that are refreshed by the system, rather than
being allowed to time out with larger traffic loss) -- but not optimized for
labratory/artificial test cases where large flows with few destinations are used.
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
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