Troubleshooting Tip: How to troubleshoot FortiGate 50G-5G modem flapping issue

Consider the manual carrier-config below:

config system 5g-modem
    config data-plan
        edit "vodafone"
            set apn "internet"
        next
    end
    config modem1
        set network-type 4g|5g
        set sim1-pin 1234
        set sim1-data-plan "vodafone"
        set carrier-config manual
    end
end

execute 5g-modem carrier-config switch 1 <----- Generic PTCRB.

Despite having set the carrier-config manually, the nr5gd debug below shows constant flapping:

[NR5G_MODEM1]MDM_IPV4_drop(1106)-1653: MDM_IPV4_drop event triggered, current state:ST_MODEM_CONNECTED
[NR5G_MODEM1]modem1_ipv4_data_call_cb(2707)-1653: data call status QMI_WDS_DATA_CALL_TERMINATED
[NR5G_MODEM1]MDM_IPV4_drop(1106)-1653: MDM_IPV4_drop event triggered, current state:ST_MODEM_CONNECTED
[NR5G_MODEM1]modem1_ipv4_data_call_cb(2707)-1653: data call status QMI_WDS_DATA_CALL_TERMINATED

To proceed with the troubleshooting process, gather the information below and open a ticket with TAC Support:

1. Collect nr5gd debug:

diagnose debug disable
diagnose debug reset
diagnose debug console time enable
diagnose debug application nr5gd -1
diagnose debug enable

To disable the debug, use the command:

diagnose debug disable

2. Configuration file.
3. TAC report.
4. System event logs.

This issue will be resolved in v7.4.10 and v7.6.5.

In addition, a fix for static IP flapping issues will be available in v7.4.12, v7.6.7, and v8.0.0.