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output drops with interface utilization = 20% !!! in Sw 2960-S

mohamed louhab
Level 1
Level 1

hi ,

i noticed the "output drops" increasing in  interface gi 1/0/1 in my switch 2960-S although the utilization of my interface is between 20% and 50 %

SW__A#sh interfaces gigabitEthernet 1/0/1

GigabitEthernet1/0/1 is up, line protocol is up (connected)

  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

     reliability 255/255, txload 93/255, rxload 3/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 1000Mb/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 00:00:00, output 00:00:00, output hang never

  Last clearing of "show interface" counters 00:10:00

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 78484

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  30 second input rate 14786000 bits/sec, 22426 packets/sec

  30 second output rate 365630000 bits/sec, 42896 packets/sec

     6584758 packets input, 575696417 bytes, 0 no buffer

SW__A#sh controllers gigabitEthernet 1/0/1 utilization

Receive Bandwidth Percentage Utilization   : 3

Transmit Bandwidth Percentage Utilization  : 50

SW_A#sh interfaces gigabitEthernet 1/0/1 | include Total output drops

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 585722

SW_A#sh controllers gigabitEthernet 1/0/1 utilization               

Receive Bandwidth Percentage Utilization   : 1

Transmit Bandwidth Percentage Utilization  : 24

The IOS version is :

Switch Ports Model              SW Version            SW Image                

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

*    1 28    WS-C2960S-24TD-L   12.2(55)SE5           C2960S-UNIVERSALK9-M    

what is the cause of this issue ??

thank you

20 Replies 20

Even if the other switch is sending pause frames, the 2960S is ignoring them,

Good point, Paolo.

Ok , thank you for all this explanation

so it 's possible to enable flow-control in the switch 2960s ?

thank you ,

hi ,

i have found it

interface Gi 1/0/1

flowcontrol  receive on

flowcontrol  send on

i will test that and i will send to you the result

thank you

Hi ,

when i activate "flowcontrol " on the interface ( by the command flowcontrol receive on) i noticed that the interfaces of the router ( ASR-1001) conneceted to this Switch  Become "shut down " !!!!


I did not understand why??? !!

It doesn't really matter, as flow control does not help at in case of output drops.

mohamed louhab
Level 1
Level 1

Hi ,
Yes the qos is disabled in the switch.

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