How to check the status of optical modules on Cisco devices

Use Cisco CLI commands like show interface transceiver detail, show inventory, and show idprom to monitor SFP health, link status, and optical diagnostics.

Step 1: Access the Device

SSH or console into your Cisco switch or router. Enter Privileged EXEC mode using enable and your credentials.

Step 2: Verify Port and Link Status

• Run show interface status to see all ports, their link status (up/down), speed, duplex, and media type. This quickly confirms whether the port recognizes the SFP module and is operational .
• For detailed interface information, use:

  show interface <interface-id> This displays negotiation speed, link type, media type, and traffic statistics .

Step 3: Check Installed Modules

• Use show inventory to list all installed hardware, including SFPs, with Product ID (PID), Version ID (VID), and Serial Number (SN) .
• If a module does not appear, reseat it or verify compatibility.

Step 4: View Transceiver Diagnostics (DOM/DDM)

• For Catalyst switches:

  show interface <interface-id> transceiver detail This provides Digital Optical Monitoring (DOM) metrics such as:

  • Transmit (Tx) and Receive (Rx) power in dBm
  • Temperature in °C
  • Voltage in V
  • Bias current in mA
• For Small Business or SMB switches:

  show fiber-ports optical-transceiver This shows similar optical metrics including output power and current consumption .

Step 5: Read Module EEPROM and Vendor Information

• Use:

  show idprom interface <interface-id> or

  show idprom transceiver extended This displays EEPROM data including vendor name, part number, serial number, wavelength, and transceiver type .

Step 6: Troubleshoot Unsupported or Err-Disabled Modules

• If a port shows err-disabled due to an unsupported transceiver, check logs:

  show logging | include <interface|transceiver|unsupported>

• To allow third-party modules (use with caution):

  no errdisable detect cause gbic-invalid Ensure the module is high-quality and compatible with Cisco devices .

Step 7: Monitor and Maintain

• Periodically check SFP health to detect degradation early.
• Compare Tx/Rx power against Low/High warning thresholds; replace or clean connectors if readings exceed limits . By following these steps, you can effectively monitor, diagnose, and maintain optical modules on Cisco devices, ensuring stable network performance and early detection of potential issues.