Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

switch interface output discards

Hello all.

I have a Cisco 2960G router connected to a 3745 router. the configuration for the switch interface is as below

interface GigabitEthernet0/1

description connected to CORE ROUTER

switchport mode access

srr-queue bandwidth share 10 10 60 20

queue-set 2

priority-queue out

mls qos trust cos

auto qos voip trust

I dont really understand the QoS commands. When i do "show interface g0/1" i am seeing too many output drops on the interface. What could be causing this?

Everyone's tags (3)
Super Bronze

Re: switch interface output discards


The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.


Usually drops are from lack of buffers.  The cause is more traffic sent to the interface then the interface can transmit.  If it's long term oversubscription, drops are often normal.  If traffic is rate adaptive, drops often are used to signal sender to slow its transmission rate.  (NB: for these cases, the ideal drop rate is such that it's the minimum number of drops to regulate transmitter to available bandwidth; often a drop rate of up to about 1%.)

If it's short term oversubscription, allocated buffers are likely insufficient for the needs of your traffic.  If possible, increased buffer alloction might mitigate or eliminate the drops.

CreatePlease to create content