i am getting output drops on switch actually i have ethercannel bundleing 4 ports and those are connecting to our hyperV server. We have schedule mirror images to one of our another server everyday So whenever transfer start we get alert from our Opmanager that discard rates of interface reaching to 80% File transfer is quite big i have checked interface cournters and i see output drops is also too high

here are some show commands results

show inter po12
Port-channel12 is up, line protocol is up (connected)
  Hardware is EtherChannel, address is 0045.1d05.e10e (bia 0045.1d05.e10e)
  Description: Link Aggregation Channel on (VRTX A) Master and Slave on Port 1/0/14,16, 2/0/14,16 (HOSTA02)
  MTU 1500 bytes, BW 4000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, link type is auto, media type is
  input flow-control is off, output flow-control is unsupported
  Members in this channel: Gi1/0/14 Gi1/0/16 Gi2/0/14 Gi2/0/16
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output 00:00:00, output hang never
  Last clearing of "show interface" counters 20:13:25
  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 35357406
  Queueing strategy: fifo
  Output queue: 0/0 (size/max)
  5 minute input rate 1292000 bits/sec, 227 packets/sec
  5 minute output rate 1208000 bits/sec, 330 packets/sec
     94073330 packets input, 117676230666 bytes, 0 no buffer
     Received 22188 broadcasts (9166 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 9166 multicast, 0 pause input
     0 input packets with dribble condition detected
     62893972 packets output, 50371697251 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

show run int po12
Building configuration...
interface Port-channel12
  switchport mode trunk
 spanning-tree bpduguard enable

show interfaces po12 counters errors

Port        Align-Err     FCS-Err    Xmit-Err     Rcv-Err  UnderSize  OutDiscards
Po12                0           0           0           0          0     35357406

Port      Single-Col  Multi-Col   Late-Col  Excess-Col  Carri-Sen      Runts
Po12               0          0          0           0          0          0

We have not configured QOS or strom control so far any suggestions please ???

  • 1
    Please edit your question to include the full configuration.
    – Ron Maupin
    Oct 16, 2018 at 17:31
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Dec 31, 2020 at 20:41

2 Answers 2


Output queue: 0/0 (size/max)

Someone has gotten cute and disabled the output queue. If the frame cannot be forwarded immediately ("zero delay"), it's dropped. Obviously, Don't Do That™. (they're also playing with the input queue as the default isn't 2000.)

You'll see something like hold-queue 0 out in the interface configuration.

  • Nice catch! I would've missed that one! Why would anyone do such a thing? Is that some "good advice" for some obscure use case that was once described somewhere in a forum and has been handed down for many generations? Oct 16, 2018 at 19:18
  • I'm a "good" network engineer. I don't know what's running through the mind of the "bad" network engineers that do stuff like this.
    – Ricky
    Oct 17, 2018 at 18:34

Packets are getting in queue because of throughput issue on switch interfàce . Files are unable to forward because of congestion in network resulting in high bandwidth utlization on networks to overcome this issue increase throughput of interface and test connectivity at the same time check ,memory , processor resources utlization on 3850 Switch .

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