Learn how to check SFP module health on Cisco switches. This guide covers essential CLI commands (show inventory, DOM), fixes for "unsupported transceiver" errors, and interpreting optical power levels. When optical modules operate on a switch, it is usually necessary to read the module's internal information to understand its working status—such as connection status and real-time metrics like optical power and temperature. Additionally, identifying module information helps detect coding. This guide gives a practical, CLI-focused workflow for checking SFP health and diagnostics on Cisco switches, shows the exact commands you'll use, explains what the numbers mean, and compares OEM (Cisco) vs third-party modules so you can pick the right SFP module supplier for reliability and cost. An important factor is to make sure that Cisco-compatible transceivers are fully compatible with your Cisco switch. Steps described here will be based on CISCO NX-OS. First step would be to know your switch or router and what kind of transceivers. Monitoring the optical power of SFP (Small Form-factor Pluggable) modules is a critical step in maintaining stable network links. Even if an interface appears up, degraded Tx/Rx levels can cause intermittent flapping, packet loss, or err-disabled states. Checking optical power helps pinpoint issues.