Technical Tip: Understanding the log message 'Modem failed to open'

The sample system event message will be looked like below:

type="event" subtype="system" level="information" vd="root" logdesc="Modem failed to open" msg="modem: unable to open modem device - check hardware"

This message says the 3G/4G modem connected to the FortiGate via the USB slot failed to open. Use the following debug command to check the status of the LTE modem:

diagnose sys lte-modem info

Additional information:

1. This error message can be an expected behavior and not a bug when the FortiGate has no LTE modem connected to the FortiGate but it was enabled on the CLI.
2. The error message will keep appearing until the modem is successfully connected OR the configuration is removed.

To avoid this error message being generated unnecessarily and confusing, make sure the following configuration is disabled if it is not being used:

• Disabling the modem status.
  
  

config system modem

    set status disable

end

• Remove any firewall address object associated with the modem.
  
  

config firewall address

    edit "THE ADDRESS ASSOCIATED TO MODEM"

    unset associated-interface

    next