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New Member

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.



New Member

Re: interface resets and CRC errors

I think this is a result of your interface being set at 10/half. See if you can hard code if for full duplex on both ends.

New Member

Re: interface resets and CRC errors

Thanks for the replay. I have to talk to my ISP because on my router the duplex is setup to auto and if I change it to full interface goes down...

New Member

Re: interface resets and CRC errors

CRC + Interface resets are layer 1 issues , get to isp to check the line / else see what speed /duplex does modem takes and change accrodingly on router ..

rate if helps

New Member

Re: interface resets and CRC errors

You need to check the service provider. Have end to end loopback testing hop by hop. CRC errors could be due to bad line, clock sync problem etc.

In order to eliminate that it is not a router interface problem use a loopback on router interface and see if you see get CRC and Interface errors. If not it is a service provider problem

rate if it helps

New Member

Re: interface resets and CRC errors

Hi guys,

Thank you for your answers. You're right :)

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.


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