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Cisco CRC Error

Viewing 5 posts - 1 through 5 (of 5 total)
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  • #31133

    Hi guys,
    I’m experiencing a problem that is driving me crazy.
    I have a Cisco AS5350 and a 3700 router series used as GK.
    On both machines if I run a ‘show interface fastethernet 0/1’ I can see a lot of CRC error and only on the AS5350 also frame error.
    I already changed the hub and the cables but the problem persist.

    Hope someone could give me some hints.

    Thanks a lot…

    Alex Z


    Please post the FULL output from “show interface fast0/1”.

    Most ethernet problems arise from bad cabling or duplex mismatch.

    You can use following links for troubleshooting:


    Hi Alex, thank you very much for your reply. Unfortunatly I can open your links. In any case I changed the duplex to half and now the CRC error are decreased by 95% but instead collision have started to rise 🙁

    this is the show int:
    FastEthernet0/1 is up, line protocol is up
    Hardware is Fast Ethernet, address is 000f.f7d0.496d (bia 000f.f7d0.496d)
    Internet address is
    MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
    reliability 255/255, txload 2/255, rxload 4/255
    Encapsulation ARPA, loopback not set
    Keepalive set (10 sec)
    Half-duplex, 100Mb/s, 100BaseTX/FX
    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: 2/4096/0/0 (size/max/drops/flushes); Total output drops: 0
    Queueing strategy: fifo
    Output queue: 0/4096 (size/max)
    5 minute input rate 1866000 bits/sec, 2684 packets/sec
    5 minute output rate 1091000 bits/sec, 1406 packets/sec
    192817259 packets input, 1847950642 bytes
    Received 8007 broadcasts, 0 runts, 0 giants, 0 throttles
    111530 input errors, 111530 CRC, 25125 frame, 0 overrun, 0 ignored
    0 watchdog
    0 input packets with dribble condition detected
    122369142 packets output, 1210563845 bytes, 0 underruns
    334 output errors, 8139613 collisions, 4 interface resets
    0 babbles, 334 late collision, 4092325 deferred
    0 lost carrier, 0 no carrier
    0 output buffer failures, 0 output buffers swapped out


    Alex Zhilyakov


    Collisions are normal events in shared Ethernet environment. You will virtually always see them in Half-Duplex ethernet operation.

    It seems that your hub does not support full-duplex (and if it did, it would be switch then). If error counters do not increase anymore, just collisions, then you are fine.

    If your collision rate rises above 10-20%, think about replacing the hub with a full-duplex switch.


    Thank you very much for the reply.
    I will plan to buy a switch.

Viewing 5 posts - 1 through 5 (of 5 total)
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