How to handle CRC errors ? Highlighted

Created: Oct 18, 2018 10:16:50Latest reply: Oct 30, 2018 16:37:17 1179 11 10 0
This post was last edited by Finn92 at 2018-10-18 10:36.
ssue Description
Fault symptom: Switch is reporting a lot of CRC error on some interfaces and some packets are lost due to this issue.
You can use display interface xxxx to check the CRC errror statistics .
 Solution
Most probably, the CRC issue is caused by the hardware part, it is not a software issue. There are some reasons which can cause CRC issue, such as the transceiver is not inserted tightly, the fiber or cable is twisted too much, the transceiver is unstable, or the hardware of this port is unstable on the Switch.


To handle the CRC issue, the best way is to do the cross-test:
1. first check the transceiver and fiber, if they are tightly connected. You can plug out and plug in to test again.
2. move the transceiver to other ports on the switch, if the CRC still persists, it means that the CRC is related to transceiver or fiber. If CRC disappears, it means that maybe the hardware of this port is unstable, we can find another good transceiver to test again, if the CRC still happens even if we replace with another good transceiver. In this case, we can replace the switch.
3. after the step2, if the CRC still happens even after moving to other ports, it means that this may be related to transceiver issue. We can replace with another good transceiver, if the CRC disappears then it's related to faulty transceiver.


CRC may be related to peer device also in case that the transceiver is not connected to peer switch tightly or the hardware of the port is unstable on peer switch. We can find another good transceiver to test on peer switch, if the CRC still happens even if we test with another good transceiver, we can say the hardware of this port is unstable.
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yjhd     Created Oct 18, 2018 10:18:03 Helpful(0) Helpful(0)

This post was last edited by yjhd at 2018-10-31 15:43.

CRC error means physical link has problem? if so, maybe solved one issue of mine

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Torrent     Created Oct 18, 2018 10:21:52 Helpful(0) Helpful(0)

This post was last edited by Torrent at 2018-10-31 15:21.

The crc-alarm enable command enables the alarm function for CRC errors on the AP wired interface and specifies the alarm threshold and clear alarm threshold.

The undo crc-alarm enable command disables the alarm function for CRC errors on the AP wired interface and restores the alarm threshold and clear alarm threshold to the default values.

By default, the alarm function for CRC errors is disabled on the AP wired interface. The alarm threshold for CRC errors is 50 and the clear alarm threshold is 20.

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faysalji  Visitor   Created Oct 18, 2018 13:06:10 Helpful(0) Helpful(0)

Thanks for sharing
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If you think my post/reply is useful, please click the Helpful button and flag my post as a BEST ANSWER. Thanks
SupperRobin     Created Oct 18, 2018 17:20:38 Helpful(0) Helpful(0)

This post was last edited by SupperRobin at 2018-10-31 14:55. When the Device detects that the number of CRC errors exceeds the configured upper alarm threshold in a specified period, it sends an alarm message to the AC. To prevent the AP from frequently sending alarm messages or alarm clearance messages to the AC, you need to configure the lower threshold for clearing the alarm. The AP sends an alarm clearance message to the AC only when the AP detects that the number of CRC errors is lower than the configured lower threshold.
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wissal  Enthusiast Technician   Created Oct 19, 2018 01:13:16 Helpful(0) Helpful(0)

Good work, thanks
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No.9527  Visitor   Created Oct 19, 2018 11:30:05 Helpful(0) Helpful(0)

This post was last edited by No.9527 at 2018-10-31 14:46. In a stack system, if a stack port continuously receives CRC error packets or flaps between Up and Down states, the corresponding stack link cannot forward traffic normally, thereby affecting network services. This command enables the stack port error-down function. This function can shut down a stack port and switch traffic to other stack links if the rate of received CRC error packets or the number of Up/Down transitions on the stack port reaches the specified threshold, reducing the impact on services. Additionally, the system generates stack port error-down alarms to help in fault location.
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lizhi94     Created Oct 19, 2018 17:45:10 Helpful(0) Helpful(0)

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ViktorG  Visitor   Created Oct 22, 2018 15:03:25 Helpful(0) Helpful(0)

Hi there guys!
Just to update the topic:
- CRC can be related due to Fiber cable connectors are not clean enough.
- Maybe the Optical Tx/Rx level of the SFP is not Ok
- Maybe even distance between network elements is larger the SFP supported (especially Multimode SFP)
So, please, do not just change one single SFP inside single chassis - look for the whole physical path.
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Take care and have a great day!
Viktor
littlestone     Created Oct 23, 2018 12:07:04 Helpful(0) Helpful(0)

This post was last edited by littlestone at 2018-10-31 14:08. Determine the forwarding mode of packets.
  • For CE8800&CE7800&6800&5800 series switches exclude CE6870EI and CE6875EI, hash modes can be configured for known and non-known unicast packets separately. First check whether packets are known or non-known unicast packets
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