1 Reply Latest reply on Apr 3, 2019 3:08 PM by jayh

    Input errors and CRC errors on interfaces

    arashbrar2 New Member

      I am seeing input and CRC errors on WAN interface at one of branch router. Topology overview is :   WAN----> Adtran 3430 (eth 0/1) -------> Juniper 2200 (LAN via eth 0/2).

      We are using site to site VPN at this router.

      Interface configuration:


      show run int eth 0/1

      Building configuration...



      interface eth 0/1

        description Spectrum IP is ************

        speed 100

        ip address  ***************

        ip access-policy Public

        ip crypto map VPN

        no shutdown

        no lldp send-and-receive





      Here is details output for interface:


      sh int eth 0/1        

      eth 0/1 is UP, line protocol is UP

        Description: Spectrum IP is ************

        Hardware address is **************

        Ip address is **********, netmask is

        IP MTU is 1500 bytes

        BW is 100000 Kbit

        100Mb/s, full-duplex

        ARP type: ARPA; ARP timeout is 20 minutes

        Last clearing of "show interface" counters: 02:51:50

        5 minute input rate 138080 bits/sec, 29 packets/sec

        5 minute output rate 72320 bits/sec, 36 packets/sec

          Queueing method: fifo

          Output queue: 0/256/0 (size/max total/drops)

          Interface Shaper: NOT ENABLED

          426676 packets input, 238919227 bytes

          426620 unicasts, 56 broadcasts, 0 multicasts input

          0 unknown protocol, 0 symbol errors, 0 discards

          3731 input errors, 0 runts, 0 giants

          0 no buffer, 0 overruns, 0 internal receive errors

          0 alignment errors, 3731 crc errors

          463362 packets output, 131887741 bytes

          463362 unicasts, 0 broadcasts, 0 multicasts output

          0 output errors, 0 deferred, 0 discards

          0 single, 0 multiple, 0 late collisions

          0 excessive collisions, 0 underruns

          0 internal transmit errors, 0 carrier sense errors

          0 resets, 0 throttles


      Please suggest me some troubleshooting tips.

        • Re: Input errors and CRC errors on interfaces
          jayh Hall_of_Fame

          You probably have a duplex mismatch. When you specify "speed 100" that turns off auto-negotiation. The other side will then fall back to half-duplex. I would suggest that you remove the "speed 100" statement in the interface configuration. This will probably cause the interface to bounce. Then clear counters and see if the errors continue to increment.


          If this doesn't fix it or the interface doesn't recover, you may need to use a crossover cable if the other side doesn't do auto-MDI-X.


          If it still doesn't want to behave, you may need to go to the connected device on eth 0/1 and configure both sides to 100Mbits and full duplex. I bet simply removing the "speed 100" statement will fix it.


          config t

          interface eth 0/1

          no speed 100




          clear counter eth 0/1

          show int eth 0/1


          [wait a couple of minutes]


          show int eth 01


          Look for incrementing errors.