OutDiscards on CISCO7609

[thiyagarajankalaiselvan]

Hello,

I'm facing outdiscards error on the server connected interface.

Can anybody help me to fix this issue on Cisco 7609?

Regards,

Thiyagu

[Arumugam Muthaiah]

Hi Thiyagu,

Usually the Output drops represent egress traffic dropped due to momentarily exceeded wire capacity. It can be either traffic bursts or sustained high traffic rate.

1. Do you see the output drops on single interface which is connected to server?

2. Does the output drops incrementing constantly or intermittent?

could you share the below detail to understand this issue better

show version
show module
clear counters

Check the below commands multiple times and check the error status like how often it is incrementing and what type of errors seen on the interface

show interface <interface type>
show interfaces <interface type> counters errors
show queueing interface <interface type>

Regards,

Aru

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[thiyagarajankalaiselvan]

I'm finding packet drops in tranmit. Can you help me to fix the issue

#sh module

Mod Ports Card Type                              Model              Serial No.

--- ----- -------------------------------------- ------------------ -----------

  1   24  CEF720 24 port 1000mb SFP              WS-X6724-SFP       SAL10499RJ9

  2   24  CEF720 24 port 1000mb SFP              WS-X6724-SFP       SAL1419HFKC

  3    4  CEF720 4 port 10-Gigabit Ethernet      WS-X6704-10GE      SAL1435S74J

  4    4  SLB Application Processor Complex      WS-X6066-SLB-APC   SAD141003WR

  5    2  Supervisor Engine 720 (Active)         WS-SUP720-3B       SAL15024PQK

  6    4  CEF720 4 port 10-Gigabit Ethernet      WS-X6704-10GE      JAF1212ARCQ

  7   48  CEF720 48 port 10/100/1000mb Ethernet  WS-X6748-GE-TX     SAL09179VP9

  8   48  CEF720 48 port 10/100/1000mb Ethernet  WS-X6748-GE-TX     SAL1514ALRB

  9   48  CEF720 48 port 10/100/1000mb Ethernet  WS-X6748-GE-TX     SAL1219Q52J

#sh queueing interface Gi8/1

Queueing Mode In Rx direction: mode-cos

    Receive queues [type = 1q8t]:

    Queue Id    Scheduling  Num of thresholds

    -----------------------------------------

       01         WRR                 08

    WRR bandwidth ratios:  100[queue 1]

    queue-limit ratios:    100[queue 1]

    queue tail-drop-thresholds

    --------------------------

    1     100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

    queue thresh cos-map

    ---------------------------------------

    1     1      0 1 2 3 4 5 6 7

    1     2

    1     3

    1     4

    1     5

    1     6

    1     7

    1     8

  Packets dropped on Transmit:

    queue     dropped  [cos-map]

    ---------------------------------------------

    1                    77319  [0 1 ]

    2                        0  [2 3 4 ]

    3                        0  [6 7 ]

    4                        0  [5 ]

  Packets dropped on Receive:

    BPDU packets:  0

    queue              dropped  [cos-map]

    ---------------------------------------------

    1                        0  [0 1 2 3 4 5 6 7 ]

[Arumugam Muthaiah]

Hi Thiyagu,

Packets dropped on Transmit:

    queue     dropped  [cos-map]

    ---------------------------------------------

    1                    77319  [0 1 ] ---> This drops indicates the interface experienced oversubscription & dropping the packets

    2                        0  [2 3 4 ]

    3                        0  [6 7 ]

    4                        0  [5 ]

Please clear the counter and check the below commands,

show interface <interface type>
show interfaces <interface type> counters errors
show interface | include line|drops|rx|tx

does the interface seeing continous drops or intermittent?

• You can prevent output drops only if output drops are a consequence of short bursts of data. If output drops are caused by a constant high-rate flow, you cannot prevent the drops.
  
• If the packets are coming in faster than going out, eventually you will have overflow. We forward the traffic in hardware level and the hardware buffer is fixed
  
• Buffer tuning allows you to modify the way a switch allocates buffers from its available memory, and helps prevent packet drops during a temporary burst of traffic only.
  

Refer:

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a0080094791.shtml#drops

Regards,

Aru

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