This is typically due to one of the following failures: hardware defect, poor seating, or incompatibility. The result here is a down port with no data flow. This could be that the link dropped periodically or the link was unstable. Common reasons. The optical module cannot be properly identified and optical module information cannot be obtained. The working rate, duplex mode, and. Based on typical issues encountered with optical modules in daily switch applications, this document summarizes basic troubleshooting steps for resolving common faults: 1. ) are designed for high reliability in modern networks.