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hutcha4113
Beginner

Total Output Drops - Very High. Cisco C3560X

Looking for some assistance on an issue we are seeing with a Cisco C3560X.  All of our branch switches have the same configuration, however this particular Branch Switch is generating an alert in Solarwinds, with a high number of Discards.  I believe Discards in SW relate to show interface value -> Total Output Drops (I believe anyway).

Running 15.0(2) SE8 UniversalK9-M

Here is the configuration of a sample standard access port:

interface GigabitEthernet0/5

 description ****Standard Access Port****

 switchport access vlan 10

 switchport mode access

 switchport voice vlan 11

 no logging event link-status

 srr-queue bandwidth share 1 70 25 5

 srr-queue bandwidth shape 30 0 0 0

 priority-queue out

 no snmp trap link-status

 mls qos trust dscp

 storm-control broadcast level 15.00

 storm-control action shutdown

 no cdp enable

 no lldp transmit

 no lldp receive

 spanning-tree portfast

Here is the show interface for this port:

show interface gigabitEthernet 0/5

GigabitEthernet0/5 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is 6c99.89e7.9105 (bia 6c99.89e7.9105)

  Description: ****Standard Access Port****

  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX

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

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

  Last input never, output 00:00:07, output hang never

  Last clearing of "show interface" counters 1d00h

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 7844280

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 89000 bits/sec, 50 packets/sec

  5 minute output rate 239000 bits/sec, 141 packets/sec

     145793 packets input, 30710632 bytes, 0 no buffer

     Received 810 broadcasts (423 multicasts)

     0 runts, 0 giants, 0 throttles

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

     0 watchdog, 423 multicast, 0 pause input

     0 input packets with dribble condition detected

     4038005 packets output, 428508100 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

I have highlighted the total output drops, as I believe that is generating the Alert.  It is also crazy high, compared to any of our other switches.

Should also note we are using this configuration everywhere, and it works fine at other locations, with the same type of devices plugged in.  Here is an example of another Branch Office, and what its traffic looks like:

show interface gigabitEthernet 0/3

GigabitEthernet0/3 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is ccd8.c16d.2d03 (bia ccd8.c16d.2d03)

  Description: ****Standard Access Port****

  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX

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

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

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

  Last clearing of "show interface" counters never

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

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 2000 bits/sec, 3 packets/sec

  5 minute output rate 2000 bits/sec, 3 packets/sec

     2220922 packets input, 181965988 bytes, 0 no buffer

     Received 242314 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

     13828206 packets output, 1348934099 bytes, 0 underruns

     0 output errors, 0 collisions, 1 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

These switches are the same model, running the same IOS version - pretty much identical in every way, accept for the Physical Location.  Any thoughts on why I am seeing such an issue?

3 REPLIES 3
Reza Sharifi
Hall of Fame Expert

Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX

Is the device connected to port 0/5 supposed to operate at 100Mb or Gig?

Also, here is a link on troubleshooting output drops:

http://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/6343-queue-drops.html

HTH 

All devices connected to this switch are 100MB/Full Duplex.  They seem to be negotiating fine.  I should also advise it is not just port 5 on the switch - pretty much every port is generating the same thing.

haver you tried turning off mls qos , it can cause issues like this , what are the statistics for the qos queues are any of them over utilized seeing drops , have you tried tweaking the buckets in mls ? 

3560s also have very low buffers so if any of the devices connected to this are using apps which can cause burst traffic it fills the buffer instantly causing output drops , they can be legitimate depending on the traffic patterns in place

you can check for micro bursts through wire shark , it may be software rather than the switch causing it , also could be mls  

https://notalwaysthenetwork.com/2014/01/06/microburst-detection-with-wireshark/