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interface resets and CRC errors

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  • interface resets and CRC errors

    Hi guys,

    I'm getting lots of CRC's errors and interface resets on fa0/1 which is connected to the modem of the ISP. Here is a sample of "show int fa0/1" output :
    "FastEthernet0/1 is up, line protocol is up
    Hardware is Gt96k FE, xxxx
    Description: xxxx
    Internet address is x.x.x.x
    MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
    reliability 253/255, txload 1/255, rxload 4/255
    Encapsulation ARPA, loopback not set
    Keepalive set (10 sec)
    Half-duplex, 10Mb/s, 100BaseTX/FX
    ARP type: ARPA, ARP Timeout 04:00:00
    Last input 00:00:17, output 00:00:00, 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 170000 bits/sec, 111 packets/sec
    5 minute output rate 76000 bits/sec, 122 packets/sec
    1981409 packets input, 649837835 bytes
    Received 4 broadcasts, 0 runts, 0 giants, 0 throttles
    9819 input errors, 9819 CRC, 0 frame, 0 overrun, 0 ignored
    0 watchdog
    0 input packets with dribble condition detected
    1849190 packets output, 216051247 bytes, 0 underruns
    7107 output errors, 40657 collisions, 7032 interface resets
    0 babbles, 7252 late collision, 0 deferred
    0 lost carrier, 0 no carrier
    0 output buffer failures, 0 output buffers swapped out"
    I have a 1841 router, IOS v12.4(3d), release software (fc3). Why do I get those errors and what should I do to correct the situation?

    Thank you.
    Regards,

    Florin

  • #2
    Re: interface resets and CRC errors

    CRC errors are most often bad cables, or incorrect cable length.
    "...if I turn out to be particularly clear, you've probably misunderstood what I've said” - Alan Greenspan

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    • #3
      Re: interface resets and CRC errors

      Thank you for the replay.
      So...it doesn't have anything to do with the interface being half-duplex?
      On my side is set up to "duplex auto". If I change it to duplex full interface goes down.
      Regards,

      Comment


      • #4
        Re: interface resets and CRC errors

        So...it doesn't have anything to do with the interface being half-duplex?
        On my side is set up to "duplex auto". If I change it to duplex full interface goes down.
        I dont see how that would matter.
        If the modem of the ISP is set at half duplex then you have no choice but to use half (or auto). If you can change the modem to full (or auto) then you can take advantage of full duplex.
        "...if I turn out to be particularly clear, you've probably misunderstood what I've said” - Alan Greenspan

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        • #5
          Re: interface resets and CRC errors

          Hi Florin,

          there's a lot of collisions on this interface. An awful lot. I would expect a few (it is a small collision domain, after all), but not this many. I think this is where your resets are coming from. I've seen this where the interface is on the customers side and on auto.

          Just make sure that, on your side, the interface is definitely set to 10/half and not auto. Other things to try are (as stated by Lior_S) swapping out the cable for a known, good cable.

          I'm not sure what your router is plugged into. I'm assuming a switch of some description, but if not, its worthwhile getting your hands on a small, unmanaged workgroup switch (an 8 port model is very cheap these days) and inserting this between your router and whatever device its connected to.

          theterranaut

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          • #6
            Re: interface resets and CRC errors

            Hi guys,

            Thank you for your answers.
            Actualy the problem was on my ISP side. The LAN interface on their modem/router (Nortel SR 1004) was setup to half-duplex. Soon as they changed that to auto everything went back to normal, no more collisions or CRC's and the speed got where it was suppose to be, 4.1-4.2 Mbps for upload and download.
            Cheers,

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