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Cisco Bug: CSCsz07068 - VSS: Output Drops on a VSL port due to small Tx Queue limit

Last Modified

Mar 02, 2018

Products (1)

  • Cisco Catalyst 6000 Series Switches

Known Affected Releases

12.2SXH

Description (partial)

Symptom:

Intermittent traffic drop.

"Total Output Drops" under "show interface TenGig x/y" incrementing.
VSS1#show interface tengig2/6/4
TenGigabitEthernet2/6/4 is up, line protocol is up (connected)
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 50 <<===

Conditions:

- Cat6500 in VSS mode, and running 12.2(33)SXHx releases.

- Traffic flow  in issue MUST be traversing the VSL link.

- "Show queueing int tengig x/y" reports packets dropped in a Tx Queue.
   VSS1#show queueing int tengig2/6/4
   <..snip..>
    Packets dropped on Transmit:
    BPDU packets:  0
    queue              dropped  [cos-map]
    ---------------------------------------------
    1                        0  [0 1 ]
    2                        0  [2 3 4 ]
    3                       50  [6 7 ]  <<====
    4                        0  [5 ]

- "show qm port-data 2 6 4" should report 512 for Tx Queue (Q #3)  in issue.
  VSS1-sp#show qm port-data 2 6 4
   <..snip..>
  Queue Limit TX:  Q[1]:90935168   Q[2]:512   Q[3]:512   <<===

  For another port in VSL, that is NOT reporting drops.
  VSS1-sp#show qm port-data 2 6 5
   <..snip..>
  Queue Limit TX:  Q[1]:45468352   Q[2]:18187328   Q[3]:13640512 <<===
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