Cisco Support Community
Community Member

Cisco 4948 switches excessive drops


We have some issues with our 4948 switches namely there are a lot of drops on interfaces. Here is an example:

GigabitEthernet1/19 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet Port, address is 001b.d417.a792 (bia 001b.d417.a792)

  Description: USPHL0ESX18 RSA

  MTU 1500 bytes, BW 100000 Kbit, 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, link type is auto, media type is 10/100/1000-TX

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

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

  Last input never, output never, output hang never

  Last clearing of "show interface" counters 6d17h

  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 17577272

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 23000 bits/sec, 33 packets/sec

     3083 packets input, 202707 bytes, 0 no buffer

     Received 299 broadcasts (0 multicasts)

     0 runts, 0 giants, 0 throttles

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

     0 input packets with dribble condition detected

     86584193 packets output, 52059988888 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

Here is the interface configuration:

interface GigabitEthernet1/19

description USPHL0ESX18 RSA

switchport access vlan 120

speed 100

duplex full

spanning-tree portfast

The drops happen in a burst. The case was opened with TAC, but it looks like we have a run around.


Cisco Employee

Cisco 4948 switches excessive drops


Did you capture a sniffer trace of this interface while the drops were occurring? This looks like oversubscription. A capture would tell you for sure using the wireshark I/O graph feature.

Is qos enabled?



LAN-Switching TAC

Community Member

Cisco 4948 switches excessive drops

Thank you  for your esponse. We have no empty ports o use wireshark. The interesting part is that there is only one device plugged into the port. It is the RSA card for that server is only for management, so, in theory, should not have a lot of traffic. QoS is not enabled on the port.


Cisco 4948 switches excessive drops

How is the far end port configured?  Seeing you hardcoded the 4948 port the far end would have to be hardcoded also otherwise the far end will default to 100/half duplex .  Output drops usuaully means the far end cannot handle the traffic fast enough .

Community Member

Cisco 4948 switches excessive drops

Thank you for your response. The interface on the server is set to 100/full, just like the switch port. The interface does not have a lot of traffic because the RSA card is only for server management.

Community Member

Cisco 4948 switches excessive drops


Jutottál valamire az esetedben? Nekünk is van 4948-as és növekvő output drop, amit semmi sem indokol.

gigabitethernet 1/41

Power consumed by backplane : 0 Watts

Mod Ports Card Type                              Model              Serial No.


1    48  1000BaseX (SFP) Supervisor             WS-C4948          

M MAC addresses                    Hw  Fw           Sw               Status


1 001f.ca75.72c0 to 001f.ca75.72ef 1.5 12.2(31r)SGA 12.2(54)SG1      Ok 

Rövid idővel nullázás után !

* GigabitEthernet1/41      0     0    0 457632 67000    4 92921000  14218    0

* GigabitEthernet1/42      0     0    0     0 90135000  9246 13000    7    0

* GigabitEthernet1/43      0     0    0     0 1568000  786 53448000  8173    0

* GigabitEthernet1/44      0     0    0     0 1186000  315 60776000  9244    0

* GigabitEthernet1/45      0     0    0     0 4807000  1667 62027000  8756    0

* GigabitEthernet1/46      0     0    0     0 4144000  1733 58523000  8508    0

* GigabitEthernet1/47      0     0    0     0     0    0     0    0    0


Super Bronze

Cisco 4948 switches excessive drops


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The drops happen in a burst. The case was opened with TAC, but it looks like we have a run around.

If drops happen in a burst, then you might be experiencing traffic bandwidth bursts.  If so, drops can happen.

Can't run port at gig?  If not, next alternate would be increase buffer resources.

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