Troubleshooting Tip: 'Modem Error' log on FortiExtender

Description

This article describes the circumstances behind a 'Modem Error' on FortiExtender.

Scope

FortiExtender 7.4.7 and beyond.

Solution

In FortiExtender 7.4.7 and beyond, an error may be observed where it does not receive any connection:

Log:

type="event" subtype="fortiextender" level="alert" action="Modem Error" msg="FXA11 INFO: Using Generic firmware with IMSI  " logdesc="Remote FortiExtender alert activity" sn="FXA11"

In the console, the following error may be seen:

Modem 1: Cellular Data Session started successfully
please wait 15s for modem resetting.................
Modem 1: Cellular Data Session started successfully
please wait 15s for modem resetting.................
Modem 1: Cellular Data Session started successfully 

This behavior may mean a SIM card is connecting to a private network. FortiExtender blocks dhcp traffic on port 67.

Resolve this with the following commands:

config lte
    config plan
        edit ATTPlan   <----- The plan should match the carrier in use.
            set private-network enable
        next
    end
end