In my topology, I have connected spirent - traffic generator to MRV switch ( L1 switch) and then connected to CISCO switch. I am seeing some input errors on this interface. What does it mean? Does it mean that some packets are bad from spirent MRV switch. here is the show command of the interface gi 0/13.

In my topology, spirent is connected to MRV switch ( L1 switch). MRV switch interface gi 0/13 is connected to the CISCO switch interface gi 0/14. I don't see any errors on the gi 0/14 of the cisco switch. However, I see the errors on the gi 0/13 ,which is the interface coming from MRV. Does it mean that CISCO switch is telling that there is some problem in the MRV switch?

  1557336 input errors, 1557204 CRC, 0 frame, 0 overrun, 0 ignored

My quesion is what the above error indicates to me.

 c3560g_1>sh interfaces gi 0/13    
    GigabitEthernet0/13 is up, line protocol is up (connected) 
      Hardware is Gigabit Ethernet, address is 0013.c4d0.570d (bia 0013.c4d0.570d)
      Description: -- MRV, 1.1.19 --
      MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, 
         reliability 255/255, txload 1/255, rxload 1/255
      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 never, output 00:00:01, output hang never
      Last clearing of "show interface" counters never
      Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
      Queueing strategy: fifo
      Output queue: 0/40 (size/max)
      5 minute input rate 0 bits/sec, 0 packets/sec
      5 minute output rate 1000 bits/sec, 2 packets/sec
         80971440 packets input, 125278495288 bytes, 0 no buffer
         Received 0 broadcasts (0 multicasts)
         132 runts, 0 giants, 0 throttles
         1557336 input errors, 1557204 CRC, 0 frame, 0 overrun, 0 ignored
         0 watchdog, 0 multicast, 0 pause input
         0 input packets with dribble condition detected
         24289474 packets output, 36669631614 bytes, 0 underruns
         0 output errors, 0 collisions, 5 interface resets
         0 babbles, 0 late collision, 0 deferred
         0 lost carrier, 0 no carrier, 0 PAUSE output
         0 output buffer failures, 0 output buffers swapped out
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Commented Aug 7, 2017 at 18:01

2 Answers 2


If you look closely, you have 1557204 CRC errors, and 132 runts, for a total of 1557336 input errors. You may have a layer-1 problem.

The runts are frames which are too small, and the CRC errors mean that the frames didn't match what the FCS says they should be. This is a sign of corrupt frames coming into the interface. This can be caused by several things, but it is likely a layer-1 problem. You should always start troubleshooting at layer-1.


Frame check sequence errors, and packets which if your MTU is at the standard of 1514 when using the standard for ethernet on Cisco equipment are missing pieces of them. As mentioned above it is usually due to a layer one physical error. Do you get them on any other devices connected to this device? do you only get them on gi 0/13? check the cable, and do a check on the port itself. Check for duplex mismatch on the port, do a hardware diag on the actual port and trace out the physical path of where the error is and where it terminates to see if it repeats itself....if no errors are present elsewhere, it points to duplex mismatch or bad cable.

Seeing as you have a L1 switch connected to it, that could very well be a duplex issue. check the other side of the link.

Good luck in your hunt!

  • 1
    One thing missing from a duplex mismatch is collisions. That would be a dead giveaway, and, since there are none, I doubt that is the problem, although it is something to check.
    – Ron Maupin
    Commented Sep 20, 2016 at 4:39

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