Receiving excessive CRC error packets is one of the reasons that cause an interface to transit to the Error-Down state. When an Ethernet interface receives excessive CRC error packets, faults such as packet loss occur. Because the interface is still in Up state, traffic is still transmitted on the interface even if a backup link is configured.
If an interface receives CRC error packets, link faults such as packet loss occur.
Check the interface status, receive optical power of the optical module, and link quality. You are advised to change the optical module or fiber, and then check whether the interface still receives CRC error packets.
You can also find the answer in Interface Management Configurations in FAQs.
