Cisco 2911 Overrun

amigan_99 used Ask the Experts™
I am running a Cisco 2911 and as more people came into the new office - I am seeing input errors which are "overrun" errors. It looks like the port negotiated ok to Gig/Auto. Any thought what the issue could be?

oc-c2911-1#sho int gi 0/0
GigabitEthernet0/0 is up, line protocol is up
  Hardware is CN Gigabit Ethernet, address is 00f2.8b5a.daa8 (bia 00f2.8b5a.daa8)
  Description: PrimaryWANDesc_$ETH-LAN$ETH-SW-LAUNCH$INTF-INFO-GE 0/0$
  Internet address is xxxxxxxxx210/26
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 3/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full Duplex, 1Gbps, media type is RJ45
  output flow-control is unsupported, input 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 never
  Input queue: 1/75/0/56 (size/max/drops/flushes); Total output drops: 5
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 12955000 bits/sec, 1639 packets/sec
  5 minute output rate 1893000 bits/sec, 1072 packets/sec
     3103345 packets input, 3287602329 bytes, 0 no buffer
     Received 154085 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     1594 input errors, 0 CRC, 0 frame, 1594 overrun, 0 ignored
     0 watchdog, 3883 multicast, 0 pause input
     2001729 packets output, 384669985 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     2578 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     2 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out
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Distinguished Expert 2018
Number of input errors correspond to number overrun, and overruns are counter
Shows the number of times that the receiver hardware was incapable of handing received data to a hardware buffer because the input rate exceeded the receiver's capability to handle the data.
how many times buffer could not receive data. So, logical conclusion is that all input errors are caused by overruns.
Cisco - Troubleshoot Ethernet

You need to implement some form of QoS in your network. Until you think of some better solution you can at least implement some congestion avoidance mechanism (RED, WRED or DWRED), when buffer is getting full it will drop some TCP packes and avoid congestion. Since TCP traffic can recover from lost packets most likely users will not notice it. If you have VoIP in your netork you should implement different QoS mechanism.
amigan_99Network Engineer


Ok - thank you much.

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