FortiGate 3G4G: improved dual SIM card switching capabilities 7.4.1

This information is also available in the FortiOS 7.4 Administration Guide: Active SIM card switching

Real time switching from active to passive SIM cards is improved on FortiGates with a cellular modem and dual SIM cards. Now SIM cards can switch when LTE modem traffic exceeds a specified data plan limit for a specified billing period. The SIM card switches shortly after the data plan limit is exceeded.

The following commands and options can be used to configure this feature:

config system lte-modem
    set data-usage-tracking enable
    config sim-switch
        set by-data-plan enable
    end
    config data-plan
        edit <id>
            set target-sim-slot {SIM-slot-1 | SIM-slot-2}
            set data-limit <data plan limit in MB to trigger SIM card switch>
            set data-limit-alert <percentage 1 to 99 to trigger log entry>
            set billing-period {monthly | weekly | daily}
            set billing-date <1 to 31 when billing-period is monthly>
            set billing-weekday <Sunday to Saturday when billing-period is weekly>
            set billing-hour <0 to 23 when billing-period is daily>
            set overage disable
            set iccid <19 to 20 digits to specify ICCID of SIM card>
            set delay-switch-time <delay SIM card switch to a specified UTC time in format HH:MM>
        next    
    end
end

data-usage-tracking {enable | disable}	Enable tracking of data usage for the LTE modem: enable: track data usage. disable: do not track data usage. Must be enabled to configure SIM card switching based on data plan overage.
by-data-plan {enable | disable}	Enable switching of SIM cards on the LTE modem based on data plan limits: enable: allow SIM card switching when data-limit is exceeded. disable: do not switch SIM cards when data-limit is exceeded.
target-sim-slot {sim-slot-1 | sim-slot-2}	Specify which SIM slot to configure.
data-limit <integer>	Specify the data limit in MB for the SIM slot (0 - 100000, use 0 for unlimited data).
data-limit-alert <integer>	Specify at what percentage of used data-limit to trigger a log entry (1 to 99).
billing-period {month | week | day}	Specify the billing period.
billing-date <integer>	When billing-period is set to monthly, specify what day of the month the bill is issued (1 to 31).
billing-weekday {sunday | monday | tuesday | wednesday | thursday | friday | saturday}	When billing-period is set to weekly specify what day of the week the bill is issued.
billing-hour <integer>	When billing-period is set to daily specify what hour of the day the bill is issued (0 to 23).
overage {enable | disable}	Disable data usage from exceeding the configured data limit: enable: allow data usage to exceed the amount specified in data-limit. disable: do not allow data usage to exceed the amount specified in data-limit. When disabled, SIM cards are switched before the data limit is exceeded. Must be disabled to allow SIM card switching.
iccid <string>	Specify the Integrated Circuit Card Identification Number (ICCID) for the SIM card in 19 to 20 digits.
delay-switch-time <integer:integer>	Delay SIM card switch to a specified UTC time in format HH:MM.

Example

In this example, data tracking and SIM card switching by data plan are enabled for the LTE modem. Each SIM card for the LTE modem is configured with a data plan.

When traffic causes data usage to surpass the configured data limit for one SIM card, the LTE modem disconnects, and the wwan interface loses its IP address and gateway. The idle SIM card becomes active, as long as it has available data to be used. After the SIM card switch completes, the LTE modem reconnects, and the wwan interface gains its IP address and gateway again.

To configure SIM card switching by data plan overage:

1. Enable data tracking for the LTE modem:

   config system lte-modem
       set data-usage-tracking enable
   end

2. Enable SIM card switching by data plan for the LTE modem:

   config system lte-modem
       config sim-switch
           set by-data-plan enable
       end
   end

3. Configure a data plan for each SIM card on the LTE modem:

   In this example, SIM-slot-1 is configured with a data limit of 50 MB for a monthly bill issued on the 10th day of the month.

   SIM-slot-2 is configured is configured with a data limit of 60 MB for a monthly bill issued on the first day of the month.

   Data overage is disabled for both SIM card slots to allow the SIM cards to switch when the data limits are exceeded.

   config system lte-modem
       config data-plan
           edit "1"
               set target-sim-slot SIM-slot-1
               set data-limit 50
               set billing-period monthly
               set overage disable
               set billing-date 10
           next
           edit "2"
               set target-sim-slot SIM-slot-2
               set data-limit 60
               set billing-period monthly
               set overage disable
               set billing-date 1
           next
       end
   end

   When the specified data-limit is exceeded while overage is disabled, the SIM card switch is triggered. When overage is enabled, the specified data-limit can be exceeded, and a SIM card switch is not triggered. Data usage is reset after the billing period passes.

4. Monitor data usage against the data limit:

   # diagnose sys lte-modem data-usage
   Estimated LTE Modem data usage in this billing cycle:
   Active data plan:              1
   Active SIM slot:               slot-1
   Plan data limit:               60(MB)
   Plan overage status:           disable
   sim-switch.by-data-plan:       enable
   Usage:                         67(MB)
   Usage percentage:              111.67%
   Current time:                  2023-07-20 16:16:38
   Plan refresh time:             2023-08-05 01:00:00
   =============================================
   Idle data plan:                2
   Idle SIM slot:                 slot-2
   Idle Plan data limit:          100(MB)
   Idle Plan overage status:      disable
   Idle Plan Usage:               78(MB)
   Idle Plan Usage percentage:    78.00%
   Idle Plan refresh time:        2023-08-10 01:00:00

5. After the SIM card switch completes, view the active SIM card:

   # diagnose sys lte-modem sim-info
   LTE Modem SIM card information:
   Active Slot: Slot 2
   SIM state: QMI_UIM_CARD_STATE_PRESENT
   ICCID: 89302370323035043340
   IMSI: 302370605258650
   Country: Canada
   Network: Fido
   SIM PIN status: Verified