How to check the optical mode of a switch

You can check the optical mode of a switch by using CLI commands to view SFP/SFP+ transceiver details, including type, wavelength, and digital diagnostic monitoring (DDM) data.

Steps to Check Optical Mode

1. Access the Switch CLI
   • Connect via SSH, Telnet, or console cable.
   • Log in with your credentials (default for Cisco Small Business switches is cisco/cisco) .
2. Verify Port Status
   • Run show interface status to confirm the port is connected and active.
   • This command shows speed, duplex, and media type (fiber or copper) .
3. Check Transceiver Identification
   • Use show inventory to list installed SFPs, including Product ID (PID), Vendor, Serial Number, and Version ID (VID) .
   • For detailed transceiver info, run:

     show interfaces <interface-id> transceiver detail or

     show idprom interface <interface-id> This displays wavelength, optical power (Tx/Rx), temperature, voltage, and bias current .

4. Interpret Digital Diagnostic Monitoring (DDM) Data
   • DDM provides real-time metrics:
     • Tx Power: transmitted optical power
     • Rx Power: received optical power
     • Temperature: SFP operating temperature
     • Voltage: module voltage
     • Bias Current: laser current
   • These values help verify the optical mode and detect potential issues .
5. Optional: Check Module Compatibility
   • If the port shows “unsupported transceiver,” verify the module against the switch's supported SFP list.
   • Use show logging | include transceiver to detect errors or warnings .

Notes

• The optical mode (e.g., 1000BASE-SX, 10GBASE-LR) is typically indicated in the transceiver type or wavelength field.
• For Extreme switches, similar commands exist:

  show port <port_number> configurationshow ports <port_number> transceiver information detail These commands display module type, media type, and DDM diagnostics . By following these steps, you can accurately determine the optical mode, monitor transceiver health, and troubleshoot fiber connections on your switch.