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airFiber - Ethernet Negotiation Issues


This article includes the basic troubleshooting steps for failed Ethernet connections on airFiber devices.

Symptom and Steps to Troubleshoot

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Main Symptoms: 

  • Low Ethernet Negotiation.
  • No access over LAN.


  • Can access via RF interface or management radio (if applicable).
  • Can not get LAN connection via switch or router port.
  • Can not discover airFiber.

Symptom Troubleshooting Steps


1.     Is your Ethernet run longer than 100 meters?

  • Yes: Cables must be equal to or less than 100 meters long. Any longer and the cable no longer fits the Ethernet standard.

    POE devices are even more bound by this standard due to the voltage drop on longer cables. The longer the cable, the less voltage you will see at the far end of the cable, providing less power to the device that is being powered via the cable.
  • No: Continue to step 2.

2.     Are you using shielded Ethernet cables? (e.g., TOUGHCable)

  • Yes: Continue to step 3.
  • No: Shielded Ethernet Cable is a requirement. TOUGHCable or equivalent should be installed.

3. Reboot the device.

  • If rebooting solves the negotiation issues, monitor the ethernet link.
  • If negotiation issues reemerge, Continue to step 4.

4. Plug directly into PoE Injector LAN port.   

  •    Now, do you get a LAN connection on your computer?
    • Yes: Try a different switch port. Done!
    • No: Continue to step 5.

5. Replace POE injector.

  •    Now, do you get a LAN connection on your computer?
    • Yes: Dispose of the damaged PoE injector. Done!
    • No: Continue to step 6.

6. Swap the short jumper cable that runs between the PoE Injector and the computer.

  •    Now, do you get a LAN connection on your computer?
    • Yes: Dispose of the damaged short ethernet jumper.
    • No: Continue to step 7.

7. Swap the ethernet cable between the radio and POE injector.

  •    Now, do you get a LAN connection on your computer?
    • Yes: Make sure your new cable is properly installed, terminated, and secured.
    • No: Continue to step 8.

8.     Is this device colocated on a mast with an FM transmitter?

  • Yes: There is a strong possibility of line interference. This is caused because FM transmitters operate on close to the same frequency of the Ethernet cables themselves.
    • Isolate the radio from potential EMI sources or use ferrite beads with shielded Ethernet cables.
  • No: Continue to step 9.

9. If all else fails, replace the radio with a known working radio, and double check cable termination and grounding.

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