To configure network interfaces to establish two separate cellular connections using one modem.  This is often referred to as Dual Packet Data Network (PDN).

The Access Point Names (APNs) and authentication credentials used in this sample configuration are hypothetical.  However, this article assumes authentic/valid APN and credentials are used in place of the hypothetical entries.

The two APNs of the hypothetical carrier "ISP" are:

• apn.internet.isp: The APN of the public internet, no authentication method required
• apn.vpn.isp: The APN of the internal VPN, authentication requires a username and a password

In order for this configuration to function, active SIM and cellular service must be present, and the device appropriately set up.  This article also assumes the device's current configuration is default.

In device configuration, navigate to Network > Interfaces.

1. Using Modem to connect to the public internet, first Enable the interface
2. Set Match SIM by to SIM slot, or any other options that is suitable
3. Set Match SIM slot to SIM1, this sample configuration assumes SIM slot 1 contains the ISP SIM
4. Disable SIM failover
5. Enable APN list only to ensure this interface only attempts connection to the APN(s) listed in the APN list
6. In APN list > APN, set APN to apn.internet.isp
7. The rest of the fields can be default

To add APN apn.vpn.isp, a new network modem interface is required.

1. In Add Interface field, insert modem_vpn and click Add.
2. In Interface type, select Modem
3. In Zone, select External
4. In Device, select Modem
5. In Match SIM by and Match SIM slot, select SIM slot and SIM1 like Interface > Modem
6. Enable APN list only
7. In APN list > APN, set APN to apn.vpn.isp
8. Set Authentication method to Automatic
9. Insert the appropriate Username and Password into its own fields: vpnuser, vpnpasswd

When all required configurations are set, click Save at the bottom of the device configurations.