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Josiah Inubio
Beginner

[How to resolve] CRC errors

Guys,

I see many crc errors on the interface, how will I face and resolve this issue? Is there any initial fault isolation that I must do? Sometimes crc errors occur on the GigE interface. Thanks.

FastEthernet0/13 is up, line protocol is up

  Hardware is Fast Ethernet, address is 0004.4d27.66cd (bia 0004.4d27.66cd)

  Description: EDL-P-Box-NO-4

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

     reliability 250/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive not set

  Auto-duplex (Full), Auto Speed (100), 100BaseTX/FX

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 18:52:43, output 00:00:01, output hang never

  Last clearing of "show interface" counters never

  Queueing strategy: fifo

  Output queue 0/40, 0 drops; input queue 0/75, 0 drops

  5 minute input rate 12000 bits/sec, 6 packets/sec

  5 minute output rate 24000 bits/sec, 6 packets/sec

     14488019 packets input, 2783320210 bytes

     Received 345346 broadcasts, 0 runts, 0 giants, 0 throttles

     261028 input errors, 259429 CRC, 1599 frame, 0 overrun, 0 ignored

     0 watchdog, 84207 multicast

     0 input packets with dribble condition detected

     19658279 packets output, 3529106068 bytes, 0 underruns

     0 output errors, 0 collisions, 1 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

2 ACCEPTED SOLUTIONS

Accepted Solutions

Hello, please manually set both sides to 'speed 100' and 'duplex full' if its still occurring, here's reference to Cisco's document:

1. Use the show interfaces ethernet exec command to determine the status of the router's Ethernet interfaces. The presence of many CRC errors but not many collisions is an indication of excessive noise.
2. Check cables to determine whether any are damaged.
3. Look for badly spaced taps causing reflections.
4. If you are using 100BaseTX, make sure you are using Category 5 cabling and not another type, such as Category 3.

I believe Cat6 should be fine too

http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a00801f5d9e.shtml

Hope this helps

Sent from Cisco Technical Support iPhone App

Please rate useful posts & remember to mark any solved questions as answered. Thank you.

View solution in original post

HI Josiah,

Usualy CRC error will not be bcz of link/bandwidth utilization.

CRC errors are mainly Layer-1 issues, hence I would request you to check the

following physical connectivities:-

1-  Kindly change the cable connecting between these ports.

2-  Clear the counters and unshut the ports.

3-  If possible can you try swapping the ports between switches?

4-  I believe speed/duplex setting are same both the ends.

HTH

Regards

Inayath

View solution in original post

17 REPLIES 17
iskoy.istem
Beginner

check the port speed, duplex settings and the physical cable. there might be speed and duplex mismatch. is this port connected to another switch or any networking equipment or just to an endpoint? if this connected to another switch or router, ensure that speed and duplex setting are matching. please check the physical cable also.

What could be the preferred cable type that supports 100M full duplex?

hi Josiah,

CRC errors and/or late collisions can be caused by a duplex mismatch.  When one site of a link is configured on full-duplex and the other on  half-duplex you will see the CRC errors at the interface which is  configured on full-duplex.

This problem occurs also when one site of a link is configured on auto-duplex and the other fixed (full-duplex).

Duplex mismatches caused very big performance problems, so be very sure both sites of a link are configured the same.

Regarding the cables;

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/hardware/Chassis_Installation/Cat6500/0bcabcon.html#wp1003617

https://learningnetwork.cisco.com/thread/47405

HTH

REgards

Inayath

*Plz rate all usefull posts.

Hello, please manually set both sides to 'speed 100' and 'duplex full' if its still occurring, here's reference to Cisco's document:

1. Use the show interfaces ethernet exec command to determine the status of the router's Ethernet interfaces. The presence of many CRC errors but not many collisions is an indication of excessive noise.
2. Check cables to determine whether any are damaged.
3. Look for badly spaced taps causing reflections.
4. If you are using 100BaseTX, make sure you are using Category 5 cabling and not another type, such as Category 3.

I believe Cat6 should be fine too

http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a00801f5d9e.shtml

Hope this helps

Sent from Cisco Technical Support iPhone App

Please rate useful posts & remember to mark any solved questions as answered. Thank you.

Is it possible that CRC errors may occur if bandwidth is highly utilized?

HI Josiah,

Usualy CRC error will not be bcz of link/bandwidth utilization.

CRC errors are mainly Layer-1 issues, hence I would request you to check the

following physical connectivities:-

1-  Kindly change the cable connecting between these ports.

2-  Clear the counters and unshut the ports.

3-  If possible can you try swapping the ports between switches?

4-  I believe speed/duplex setting are same both the ends.

HTH

Regards

Inayath

Leo Laohoo
VIP Community Legend

reliability 250/255, txload 1/255, rxload 1/255

Gotcha!

Fix could be as easy as replacing the cable.

Can you also tell us what exactly is the switch model? 

with 250/255 reliability, what does it tells?

Reliability must ALWAYS be 255/255.  Either values should never be lower.

This means you have a faulty cable.   I can't give you any details unless you have, for example, a 2960G/2960S or a 3750G/E/X switch.

I'm getting a lot of cases about crc errors, did you encounters some of these problems?

  Rx Discards     :51688                Tx Discards : 0                  

  Rx Runts       : 0                        Rx Unknown Protos : 0          

  Rx Giants       :3                        Rx Crc Errors     :539                

  Tx CongDscrd Pkt:0                   Tx Cong Dscrd Byte:0                  

  Tx MTU Exced Pkt:0            

These are data from shown at our PE routers.

I dunno.  I still say you have a faulty cable issue.

Thanks so much

If you have another switch, with GigabitEthernet interface, I can tell you where the fault is.

2960G/S or 3750G/E/X or 3850 would be nice.

I can't verify what kind of switch were connected because its part of clients demarcation and its off limits to us. But in this case, if any switch will be, where can be the problem is?