Active SIM card switching

FortiGates with a cellular modem and dual SIM card can switch in real time from the active SIM card to the passive SIM card when any of the following issues arise with the active SIM card:

• Ping link monitor fails. The SIM switch time depends on the link monitor parameters set.

• An active SIM card cannot be detected. The SIM switch time is about 20 seconds after the SIM card is no longer detected.

• A modem disconnection is detected, and a specified interval has elapsed. The SIM switch time occurs after the specified interval.

• The LTE modem traffic exceeds the specified data plan limit for the configured billing period.

SIM card switching events are captured in the FortiGate event log.

In most cases, SIM cards come with the wireless carrier's APN, which is automatically retrieved at the first connection of the LTE modem. For these cases, you can use SIM cards for different wireless carriers in SIM slot 1 and slot 2. When one or both SIM cards require their APN settings to be configured on the FortiGate, then both SIM cards should be for the same wireless carrier because config system lte-modem currently only supports a single set apn < apn > setting.

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

config system lte-modem
    set data-usage-tracking {enable | disable}
    config sim-switch
        set by-sim-state {enable | disable}
        set by-connection-state {enable | disable}
        set by-link-monitor {enable | disable}
        set by-data-plan {enable | disable}
        set link-monitor <link-monitor-name>
        set sim-switch-log-alert-interval <interval>
        set sim-switch-log-alert-threshold <threshold>
        set modem-disconnection-time <integer>
    end
    config data-plan
        edit <id>
            set target-sim-slot {SIM-slot-1 | SIM-slot-2}
            set data-limit <integer>
            set data-limit-alert <integer>
            set billing-period {monthly | weekly | daily}
            set billing-date <integer>
            set billing-weekday {sunday | monday | tuesday | wednesday | thursday | friday | saturday}
            set billing-hour <integer>
            set overage {enable | disable}
            set iccid <string>
            set delay-switch-time <time>
        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.
config sim-switch
by-sim-state {enable | disable}	Enable switching based on active SIM card state: enable: switch to the passive SIM card whenever FortiGate cannot detect the active SIM card, such as when the active SIM card is ejected. disable: do not switch SIM cards based on state.
by-connection-state {enable | disable}	Enable switching based on the connection state of the active SIM card: enable: switch to the passive SIM card whenever FortiGate detects a modem signal loss after the modem-disconnection-time expires. disable: do not switch SIM cards based on the connection state.
by-link-monitor {enable | disable}	Enable switching when a configured link monitor fails: enable: switch to the passive SIM card when a link monitor configured with link-monitor-name fails. disable: do not switch SIM cards based on the failure of a configured link monitor.
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.
link-monitor <link-monitor-name>	Specify the name of the link monitor to use with by-link-monitor.
sim-switch-log-alert-interval <interval>	Identify what number of constant SIM card switch events will trigger an event log after the threshold in sim-switch-log-alert-threshold is met.
sim-switch-log-alert-threshold	Specify how many minutes to wait before creating an event log when the number of SIM card switches defined in sim-switch-log-alert-interval is met.
modem-disconnection-time <integer>	Specify how many seconds to wait before switching over to the passive SIM card when by-connection-state is enabled and a modem signal loss is detected.
config data-plan
target-sim-slot {sim-slot-1 | sim-slot-2}	Specify which SIM slot to configure.
data-limit <integer>	Specify the data limit for the SIM slot, in MB (0 - 100000, 0 = unlimited data).
data-limit-alert <integer>	Specify at what percentage of used data-limit to trigger a log entry (1 - 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 - 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 - 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 1

In this example, automatic SIM card switching is disabled. When disabled, the SIM card only works in the default slot1, but you can manually switch the SIM card to slot2. Event logs include details about the SIM card switch.

To manually switch a SIM card:

1. Disable automatic SIM card switching:

   config system lte-modem
       config sim-switch
           set by-sim-state disable
           set by-connection-state disable
           set by-link-monitor disable
           set sim-slot 1
       end
   end

2. Manually switch the SIM card from slot1 to slot2, and run the following command:

   # execute lte-modem sim-switch

   The SIM card switch may take a few seconds. You can run diagnose system lte-modem sim-info to check the results.

   The following log is generated after unplugging an active SIM card:

   7: date=2023-05-02 time=10:41:05 eventtime=1683049264795418820 tz="-0700" logid="0100046518" type="event" subtype="system" level="information" vd="root" logdesc="LTE modem active SIM card switch event" msg="LTE modem active SIM card slot changed to 2 by user."

Example 2

In this example, automatic SIM card switching is enabled and configured to switch based on SIM state, connection state, or link monitor state, and it includes example event logs for each scenario.

To enable automatic SIM card switching by SIM state:

1. Enable automatic SIM card switching by SIM state:

   config system lte-modem
       config sim-switch
           set by-sim-state enable
       end
   end

   With this configuration, the second SIM card becomes active when the active SIM card is no longer detected, for example, if the active SIM card is ejected. The following event logs are generated:

   5: date=2023-04-28 time=17:27:27 eventtime=1682728046989682780 tz="-0700" logid="0100046513" type="event" subtype="system" level="information" vd="root" logdesc="LTE modem data link connection event" msg="LTE modem data link changed from QMI_WDS_CONNECTION_STATUS_DISCONNECTED to QMI_WDS_CONNECTION_STATUS_CONNECTED"
   
   6: date=2023-04-28 time=17:27:17 eventtime=1682728036493684280 tz="-0700" logid="0100046512" type="event" subtype="system" level="information" vd="root" logdesc="LTE modem SIM card state event" msg="LTE modem SIM card change from QMI_UIM_CARD_STATE_ABSENT to QMI_UIM_CARD_STATE_PRESENT"
   
   7: date=2023-04-28 time=17:27:12 eventtime=1682728032589776580 tz="-0700" logid="0100046513" type="event" subtype="system" level="information" vd="root" logdesc="LTE modem data link connection event" msg="LTE modem data link changed from QMI_WDS_CONNECTION_STATUS_CONNECTED to QMI_WDS_CONNECTION_STATUS_DISCONNECTED"
   
   8: date=2023-04-28 time=17:27:11 eventtime=1682728031245682560 tz="-0700" logid="0100046512" type="event" subtype="system" level="information" vd="root" logdesc="LTE modem SIM card state event" msg="LTE modem SIM card change from QMI_UIM_CARD_STATE_PRESENT to QMI_UIM_CARD_STATE_ABSENT"

To enable automatic SIM card switching by connection state:

1. Enable automatic SIM card switching by connection state:

   config system lte-modem
       config sim-switch
           set by-connection-state enable
           set modem-disconnection-time 30
           set sim-switch-log-alert-interval 15
           set sim-switch-log-alert-threshold 5
       end
   end

   With this configuration, the second SIM card becomes active when the modem cannot establish a connection with the carrier through the active SIM card. For example, a FortiGate is in a room with poor signal quality. With this configuration, the SIM card switch is triggered after the modem is detected as disconnected for 30 seconds, and the following event log is generated:

   56: date=2023-05-01 time=11:14:56 eventtime=1682964896356933480 tz="-0700" logid="0100046519" type="event" subtype="system" level="notice" vd="root" logdesc="LTE modem active SIM card switched: modem disconnection detected" msg="LTE modem active SIM card slot changed to 2, due to modem connection down."
   
   66: date=2023-05-01 time=11:14:13 eventtime=1682964852964869400 tz="-0700" logid="0100046519" type="event" subtype="system" level="notice" vd="root" logdesc="LTE modem active SIM card switched: modem disconnection detected" msg="LTE modem active SIM card slot changed to 1, due to modem connection down."
   

   When poor signal quality causes SIM cards to frequently switch back and forth, and the flapping rate occurs more than five times within the configured 15 minute time period, an event log is triggered to record the flapping severity:

   65: date=2023-05-01 time=11:14:13 eventtime=1682964853083194400 tz="-0700" logid="0100046521" type="event" subtype="system" level="warning" vd="root" logdesc="LTE modem active SIM card slot flipped back and forth in short time" msg="LTE modem switched SIM slot 8 times in last 15 minutes, which is greater than 5 times threshold."

To enable automatic SIM card switching based on link monitor:

1. Enable automatic SIM card switching by link monitor, and specify the link monitor:

   config system lte-modem
       config sim-switch
           set by-link-monitor enable
           set link-monitor "modem"
           set sim-switch-log-alert-interval 15
           set sim-switch-log-alert-threshold 5
       end
       config system link-monitor
       edit "modem"
           set srcintf "wwan"
           set server "8.8.8.8"
           set interval 1000
           set probe-timeout 100
           set failtime 3
           set recoverytime 8
       next
   end

   With this configuration, the second SIM card becomes active when the link monitor detects the active SIM card exceeds the SLA.

2. Check the link monitor status. In this example, the link monitor status is dead:

   # diagnose system link-monitor status modem
   
   Link Monitor: modem, Status: dead, Server num(1), cfg_version=7 HA state: local(dead), shared(dead)
   Flags=0x9 init log_downgateway, Create time: Fri Apr 28 16:34:56 2023
   Source interface: wwan (19)
   VRF: 0
   Interval: 1000 ms
   Service-detect: disable
   Diffservcode: 000000
   Class-ID: 0
     Peer: 8.8.8.8(8.8.8.8) 
           Source IP(10.192.195.164)
           Route: 10.192.195.164->8.8.8.8/32, gwy(10.192.195.165)
           protocol: ping, state: dead
                   Packet lost: 11.667%
                   MOS: 4.353
                   Number of out-of-sequence packets: 0
                   Recovery times(5/8) Fail Times(1/3)
                   Packet sent: 60, received: 56, Sequence(sent/rcvd/exp): 61/61/62

   The following event log is generated when the link-monitor status is dead:

   15: date=2023-04-28 time=16:31:38 eventtime=1682724697936494139 tz="-0700" logid="0100046520" type="event" subtype="system" level="notice" vd="root" logdesc="LTE modem active SIM card switched: link monitor probe failure detected" msg="LTE modem active SIM card slot changed to 2, due to link monitor probe failures."
   
   19: date=2023-04-28 time=16:31:13 eventtime=1682724673152506599 tz="-0700" logid="0100022932" type="event" subtype="system" level="warning" vd="root" logdesc="Link monitor status warning" name="modem" interface="wwan" probeproto="ping" msg="Link Monitor changed state from alive to dead, protocol: ping."

Example 3

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