[c-nsp] Troubleshooting uncategorized output drops and errors on the 6500

[John Neiberger]

I've got another strange issue brewing. We have a 1-gig interface on a
6500 (6748 blade) that has a high number of output errors and output
drops. The drops are not queue drops. Here are the stats, one week
after clearing the counters.

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 1158860
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  30 second input rate 854000 bits/sec, 101 packets/sec
  30 second output rate 78000 bits/sec, 116 packets/sec
     97152626 packets input, 115649666904 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     90216394 packets output, 7441734020 bytes, 0 underruns
     579430 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out


Packets dropped on Transmit:

    queue     dropped  [cos-map]
    ---------------------------------------------
    1                        0  [0 1 ]
    2                        0  [2 3 4 ]
    3                        0  [6 7 ]
    4                        0  [5 ]

I haven't been able to figure out what could be causing such a high
rate of errors and drops. I have a TAC case open, but the engineer
hasn't been able to explain what we're seeing. I'm probably just going
to coordinate with the server and app owners to move this to another
link, but I'm still very curious about what could cause this behavior.

Any ideas?

Thanks,
John