Help with understanding causing of Transmit Discards

Unanswered Question
Feb 5th, 2010

Hi,

I've got a 3750-E switch and in my monitoring tool I'm seeing the following:

NODEINTERFACERECEIVE
ERRORS
RECEIVE
DISCARDS
TRANSMIT
ERRORS
TRANSMIT
DISCARDS
Node Statuscore01 Interface StatusGigabitEthernet1/0/500 errors 0 discards 0 errors 470,247 discards

I'm at a loss as to where to go with this info and what to do to fix it, can someone help please. I don't have QoS enabled and the following command shows the following:

sh controllers ethernet-controller port-asic statistics
===========================================================================
Switch 1, PortASIC 0 Statistics
---------------------------------------------------------------------------

         0 TxBufferFull Drop Count               0 Rx Fcs Error Frames       
         0 TxBufferFrameDesc BadCrc16            0 Rx Invalid Oversize Frames
         0 TxBuffer Bandwidth Drop Cou           0 Rx Invalid Too Large Frames
         0 TxQueue Bandwidth Drop Coun           0 Rx Invalid Too Large Frames
         0 TxQueue Missed Drop Statist           0 Rx Invalid Too Small Frames
        57 RxBuffer Drop DestIndex Cou           0 Rx Too Old Frames         
         0 SneakQueue Drop Count                 0 Tx Too Old Frames         
         1 Learning Queue Overflow Fra           0 System Fcs Error Frames   
         0 TxBufferFrameDesc BadCrc16            0 Rx NP Packet Count0       
         1 RxBuffer Drop DestIndex Cou           0 Rx NP Packet Count1      

         0 Sup Queue 0 Drop Frames               0 Sup Queue 8 Drop Frames   
         0 Sup Queue 1 Drop Frames               0 Sup Queue 9 Drop Frames   
         0 Sup Queue 2 Drop Frames               0 Sup Queue 10 Drop Frames  
         0 Sup Queue 3 Drop Frames               0 Sup Queue 11 Drop Frames  
         0 Sup Queue 4 Drop Frames               0 Sup Queue 12 Drop Frames  
         0 Sup Queue 5 Drop Frames               0 Sup Queue 13 Drop Frames  
         0 Sup Queue 6 Drop Frames               0 Sup Queue 14 Drop Frames  
         0 Sup Queue 7 Drop Frames               0 Sup Queue 15 Drop Frames  
===========================================================================
Switch 1, PortASIC 1 Statistics
---------------------------------------------------------------------------

         0 TxBufferFull Drop Count               0 Rx Fcs Error Frames       
         0 TxBufferFrameDesc BadCrc16            0 Rx Invalid Oversize Frames
         0 TxBuffer Bandwidth Drop Cou           0 Rx Invalid Too Large Frames
         0 TxQueue Bandwidth Drop Coun           0 Rx Invalid Too Large Frames
         0 TxQueue Missed Drop Statist           0 Rx Invalid Too Small Frames
        49 RxBuffer Drop DestIndex Cou           0 Rx Too Old Frames         
         0 SneakQueue Drop Count                 0 Tx Too Old Frames         
         0 Learning Queue Overflow Fra           0 System Fcs Error Frames   
         0 TxBufferFrameDesc BadCrc16            0 Rx NP Packet Count0       
         2 RxBuffer Drop DestIndex Cou           0 Rx NP Packet Count1      

         0 Sup Queue 0 Drop Frames               0 Sup Queue 8 Drop Frames   
         0 Sup Queue 1 Drop Frames               0 Sup Queue 9 Drop Frames   
         0 Sup Queue 2 Drop Frames               0 Sup Queue 10 Drop Frames  
         0 Sup Queue 3 Drop Frames               0 Sup Queue 11 Drop Frames  
         0 Sup Queue 4 Drop Frames               0 Sup Queue 12 Drop Frames  
         0 Sup Queue 5 Drop Frames               0 Sup Queue 13 Drop Frames  
         0 Sup Queue 6 Drop Frames               0 Sup Queue 14 Drop Frames  
         0 Sup Queue 7 Drop Frames               0 Sup Queue 15 Drop Frames  
===========================================================================
Switch 1, PortASIC 2 Statistics
---------------------------------------------------------------------------

         0 TxBufferFull Drop Count               0 Rx Fcs Error Frames       
         0 TxBufferFrameDesc BadCrc16            0 Rx Invalid Oversize Frames
         0 TxBuffer Bandwidth Drop Cou           0 Rx Invalid Too Large Frames
         0 TxQueue Bandwidth Drop Coun           0 Rx Invalid Too Large Frames
         0 TxQueue Missed Drop Statist           0 Rx Invalid Too Small Frames
         2 RxBuffer Drop DestIndex Cou           0 Rx Too Old Frames         
         0 SneakQueue Drop Count                 0 Tx Too Old Frames         
         0 Learning Queue Overflow Fra           0 System Fcs Error Frames   
         0 TxBufferFrameDesc BadCrc16            0 Rx NP Packet Count0       
   9173457 RxBuffer Drop DestIndex Cou           0 Rx NP Packet Count1      

         0 Sup Queue 0 Drop Frames         4698731 Sup Queue 8 Drop Frames   
         0 Sup Queue 1 Drop Frames        14052783 Sup Queue 9 Drop Frames   
         0 Sup Queue 2 Drop Frames          231710 Sup Queue 10 Drop Frames  
   7274136 Sup Queue 3 Drop Frames          880238 Sup Queue 11 Drop Frames  
         0 Sup Queue 4 Drop Frames               0 Sup Queue 12 Drop Frames  
         0 Sup Queue 5 Drop Frames               0 Sup Queue 13 Drop Frames  
       493 Sup Queue 6 Drop Frames               0 Sup Queue 14 Drop Frames  
       588 Sup Queue 7 Drop Frames               0 Sup Queue 15 Drop Frames 

Thanks in advance

Dan

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nsn-amagruder Fri, 02/05/2010 - 06:10

TX Discards usually indicate more data being transmitted than can be buffered by the switchport.  What was the throughput according to your monitoring tool at the time of discards?  This looks like a VSS setup, is that correct?  What is connected to the other end of the switch?

Joel Singh Thu, 02/25/2010 - 13:42

am getting TxBufferFull Drop Counts incrementing.

any way to stop them , clear them

am getting them for port asic 0 switch 2

bkoch1 Tue, 07/22/2014 - 11:20

I'm having the same issue. I have a 2960S-48TS-L switch. I have 2 of the SFP modules connected via SM fiber to our 6509-E VSS on an etherchannel (mode on, not mode auto). The input copper ports are our Cisco 5508 Wireless controllers, so data is coming from the controllers and transmitting to the core switch.

Traffic out on one port is 150Mbps, and the other port is 70Mbps. Since these are gig ports, I'm not sure how they can be overloaded.

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