Direct IP support for LTE/4G

Direct IP is a public IP address that is assigned to a computing device, which allows the device to directly access the internet.

When an LTE modem is enabled in FortiOS, a DHCP interface is created. As a result, the FortiGate can acquire direct IP (which includes IP, DNS, and gateway) from the LTE network carrier.

Since some LTE modems require users to input the access point name (APN) for the LTE network, the LTE modem configuration allows you to set the APN.

LTE modems can only be enabled by using the CLI.

DHCP relay packet flow through the modem interface can be enabled from the CLI using the dhcp-relay command. config system lte-modem set dhcp-relay enable end

To enable direct IP support using the CLI:

1. Enable the LTE modem:

   config system lte-modem
     set status enable
   end

2. Check that the LTE interface was created:

   config system interface
     edit "wwan"
       set vdom "root"
       set mode dhcp
       set status down
       set distance 1
       set type physical
       set snmp-index 23
     next
   end

   Shortly after the LTE modem joins its carrier network, wwan is enabled and granted direct IP:

   config system interface
       edit wwan
           get
   name                : wwan
   ....
   ip                  : 100.112.75.43 255.255.255.248
   ....
   status              : up
   ....
   defaultgw           : enable
   DHCP Gateway        : 100.112.75.41
   Lease Expires       : Thu Feb 21 19:33:27 2019
   dns-server-override : enable
   Acquired DNS1       : 184.151.118.254
   Acquired DNS2       : 70.28.245.227
   ....

   PCs can reach the internet via the following firewall policy:

   config firewall policy
     edit 5
       set name "LTE"
       set srcintf "port9"
       set dstintf "wwan"
       set srcaddr "all"
       set dstaddr "all"
       set action accept
       set schedule "always"
       set service "ALL"
       set utm-status enable
       set fsso disable
       set nat enable
     next
   end

Sample LTE interface

When an LTE modem is enabled, you can view the LTE interface in the GUI and check the acquired IP, DNS, and gateway.

To view the LTE interface in the GUI:

1. Go to Network > Interfaces.

2. Double-click the LTE interface (wwan) to view the properties.

3. Look in the Address section to see the Obtained IP/Netmask, Acquired DNS, and Default Gateway.

4. Click Return.

To configure the firewall policy that uses the LTE interface:

1. Go to Policy & Objects > Firewall Policy.

2. Edit the LTE policy.

3. In the Outgoing Interface field, select the interface (wwan in this example).

4. Configure the rest of the policy as needed.

   

5. Click OK.

Limitations

• Most LTE modems have a preset APN in their SIM card. Therefore, the APN does not need to be set in the FortiOS configuration. In cases where the internet cannot be accessed, consult with your carrier and set the APN in the LTE modem configuration (for example, inet.bell.ca):

  config system lte-modem
    set status enable
    set apn "inet.bell.ca"
  end

• Some models, such as the FortiGate 30E-3G4G, have built-in LTE modems. In this scenario, the LTE modem is enabled by default. The firewall policy via the LTE interface is also created by default. Once you plug in a SIM card, your network devices can connect to the internet.

  Sample FortiGate 30E-3G4G default configuration:

  config system lte-modem
    set status enable
    set extra-init ''
    set manual-handover disable
    set force-wireless-profile 0
    set authtype none
    set apn ''
    set modem-port 255
    set network-type auto
    set auto-connect disable
    set gpsd-enabled disable
    set data-usage-tracking disable
    set gps-port 255
  end
  

  config firewall policy
  ....
    edit 3
      set srcintf "internal"
      set dstintf "wwan"
      set srcaddr "all"
      set dstaddr "all"
      set action accept
      set schedule "always"
      set service "ALL"
      set nat enable
    next
  end