If possible, remove and reinstall the optical modules to check whether the fault is rectified. This document describes how to determine why a port or interface experiences problems. There are no specific requirements for this document. However, the display interface command output shows that packet loss occurs on the corresponding interface due to CRC errors. Those messages tell you what the switch detected (authentication mismatch, bad EEPROM, unsupported part number, PHY disagreement) and point to a small set of concrete checks. Based on typical issues encountered with optical modules in daily switch applications, this document summarizes basic troubleshooting steps for resolving common faults: 1. Check compatibility between the optical module and switch Most switch brands have specific compatibility requirements. As core components in high-speed data networks, optical transceivers enable communication between switches, routers, and servers through fiber optic links. Despite their robust design, these modules can experience failures due to environmental stress, contamination, or incompatibility. SONET (Synchronous Optical NETwork).