Technical Tip: WWAN interface is Down after the Firmware Upgrade of FortiGate

[mkhabbazi]

Description	This article addresses the issue where WWAN/LTE connection may become unavailable following a FortiGate upgrade.
Scope	FortiGate-3G/4G modem v7.4.7 or  v7.6.2.
Solution	After upgrading the FortiGate to v7.4.7 or v7.6.2, the device will try to establish IPV6 data sessions but carriers like Firstnet/ATT do not support IPV6 PDP on APNs and cannot provision an LTE connection.  Below is an example of the error captured from the LTE debug on FortiGate.  diagnose test application lted 20  di test app lted 3  update_modem_status(544)-234: Modem activated success but connection check fails! 544    #usb_qmi_wwan_active_modem(868)-234: Activate modem! PDP Type: QMI_WDS_PDP_TYPE_IPV4_OR_IPV6  #usb_qmi_wwan_set_ip_family(244)-234: Set IP family QMI_WDS_IP_FAMILY_IPV6 for client 19  #Call end Verbose reason =  QMI_WDS_VERBOSE_CALL_END_REASON_TYPE_INTERNAL, Q  MI_WDS_VERBOSE_CALL_END_REASON_INTERNAL_PDN_IPV6_CALL_DISALLOWED  Modem activation failed!  On Firmware versions before v7.4.5, there is no option to choose pdptype. On firmware v7.4.5 and above, there is an option to select the pdptype ‘IPV4’  Configure the pdptype to address this issue.    config sys lte-modem      set pdptype IPV4     end    A reboot of the lte modem must be performed after the above change is applied.    exe lte-modem cold-reboot    Post reboot, verify that the following output displays a Connected status: di sys lte-modem data-session-info  IPV4 connection : QMI_WDS_CONNECTION_STATUS_CONNECTED   Note: In v7.4.x and v7.6.x, auto-connect can conflict with the internal modem profile negotiation. With auto-connect enable, FortiGate tries to automatically negotiate the connection as soon as the modem registers, using any profile detected, and often ignores the pdptype IPv4 inthe  setting and still attempts IPv6 or IPV4/V6. By disabling auto-connect, the FortiGate will be forced to wait until the manual connection (diagnose sys lte-modem connect) or traffic trigger, and in that manual process, the profile configuration is applied more accurately, including PDP type. config system lte-modem     set force-wireless-profile < Wireless profile ID>     set auto-connect disable end After that, the WWAN interface will be up.