How to resolve CRC errors
Use below command to check CRC errors in CICO IOS.
Command :- show interfaces fastEthernet x counters errors
Command :- show interfaces fastEthernet x
CRC errors are mainly Layer-1 issues, for layer 1 issue check following physical connectivity:-
1- 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).
insure that speed and duplex setting are same at both the ends.
2- Check cables to determine whether any are damaged, if damaged, change the cable connecting between these ports.
4- If you are using 100BaseTX, make sure you that you are using Category 5 cabling and not another type, such as Category 3.
5- Monitor the level of frame errors over time. If they are increasing, try swapping interfaces and or ports to identify the problem.
6- Clear the counters then, shut and unshut the ports.
For more information follow below link.