Actually he should be concerned ...I am not a QOS expert but , a misconfigured QOS can cause asic level drops ... you may try to disable qos on all the interfaces that are using this asic .

After that please check if the drops are still incrementing or not .

If its not because of QOS then this is a hardware issue , asic limitation .

It may be the desired behaviour - i.e. congestion avoidance. The 3560/3750 uses congestion avoidance (random dropping) when thresholds are being reached in queues, this can be a desired behaviour to slow down flows if TCP traffic is mapped to that queue/threshold.

Andy

We had a similar issue due to a misconfigured QoS and had to tweak the thresholds to rectify it.

Check whether the counters are increasing as you cannot clear them without a reload.

HTH

Narayan

Hi

We don't have any QoS in use, but I see a high number of drops when the load increases to over 600Mbit/s on that interface. See:

show platform port-asic stats drop g1/0/26

  Interface Gi1/0/26 TxQueue Drop Statistics
    Queue 0
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 1
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 2
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 3
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 3529272
    Queue 4
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 5
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 6
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 7
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0

And here the interface:

sh int g1/0/26

GigabitEthernet1/0/26 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is 0026.9981.e11a (bia 0026.9981.e11a)

  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,

     reliability 255/255, txload 17/255, rxload 2/255

  Encapsulation ARPA, loopback not set

  Keepalive not set

  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP

  input flow-control is off, output flow-control is unsupported

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 00:00:04, output 00:00:00, output hang never

  Last clearing of "show interface" counters 00:19:07

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 150

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 10629000 bits/sec, 6922 packets/sec

  5 minute output rate 67813000 bits/sec, 10457 packets/sec

     16633696 packets input, 2137400609 bytes, 0 no buffer

     Received 111580 broadcasts (56109 multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog, 56109 multicast, 0 pause input

     0 input packets with dribble condition detected

     28212625 packets output, 35494347176 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 unknown protocol drops

     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

sh mls qos

  QoS is disabled globally

sh int g1/0/26
GigabitEthernet1/0/26 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0026.9981.e11a (bia 0026.9981.e11a)
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 17/255, rxload 2/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:04, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:19:07
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 150
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 10629000 bits/sec, 6922 packets/sec
  5 minute output rate 67813000 bits/sec, 10457 packets/sec
     16633696 packets input, 2137400609 bytes, 0 no buffer
     Received 111580 broadcasts (56109 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 56109 multicast, 0 pause input
     0 input packets with dribble condition detected
     28212625 packets output, 35494347176 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     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

sh mls qos
  QoS is disabled globally

It's actually in a portchannel with a second interface, which doesn't show any errors.

Could that be a broken hardware?

It's a stack consisting of two WS-C3750E-24TD with software 12.2(58)SE1.

Thanks

Interestingly we have the same build version on 3750-x stack and observing crazy amount of packet discards on some interfaces.

Without QoS enabled?

Even without QoS, I suspect the 3750 likely does its interface buffer management similar as it does with QoS, but probably w/o reservations per interface egress queues.

If had some fantastic success with QoS enabled and after buffer tuning.  I.e. had a couple of SAN ports having multiple drops per second, after buffer tuning, just a few drops per day.

What I did was place almost all the buffers into the shared/common pool, i.e. stopped buffers being reserved per interface egress queue.  Also increased what an interface was allowed to dynamically allocate from the shared/common pool.  (Of course, understand, this better supports just a few ports with large micro bursts while other ports don't need buffers.)

Thanks for the great Info and reply.

Do you think Updating the firmware to a more recent one will fix this?