Fault symptom: Switch is reporting a lot of CRC error on some interfaces and some packets are lost due to this issue.
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.