Configuring Cellular Modems

Ixolate supports a wide range of USB and miniPCIe cellular modems that can be used as primary internet (WAN) connection or as failover for a fixed/ethernet connection.

With this guide we show you how to easily add a new modem and configure it to be used as primary WAN connection.

Supported devices

In general, Ixolate should support all cellular modems that are supported by the respective FreeBSD kernel (see latest https://cgit.freebsd.org/src/tree/sys/dev/usb/serial/u3g.c#n197). However, not all devices behave the same way, you might have to tweak your card with specific AT commands, for example in the init string.

The screenshots in this guide are for a Huawei ME909u-521 miniPCIe cellular modem.

Choosing the right hardware

Depending on the country you want to use the modem in, you might need a different cellular modem. mPCIe cards are rather expensive so make sure you get a device that supports the LTE bands of the country and provider you want to work with. Use websites like FrequencyCheck to find the frequency band(s) used and get a cellular modem that supports these frequencies.

You should also buy an appropriate pigtail antenna cable and LTE antenna. Note that LTE antennas often have different connectors than Wi-Fi antennas, chose your equipment accordingly. Getting the right antenna has a big impact on the quality of your signal. For LTE, MIMO (multiple input, multiple output) antennas should be considered, see for example this guide.

Step 1 - Talking to the cellular modem

First, we need to figure out what device is accepting AT commands on your modem. For the Huawei modem used in this example the device is /dev/cuaU0.0, other modems might provide the AT interface on another device.

On FreeBSD, /dev/cuauN devices are call-out ports that are used for modems instead of terminals, see section 26.2.1 in the FreeBSD manual.

The best way to locate the correct port is to send AT commands to it. This can be tested using the utility cu:

cu -l /dev/cuaU0.2
Connected
AT (<-type that)
OK

Once you see Connected type AT. If you do not get an OK back, enter ~. to quit and try the next device. In this particular example, a Sierra Wireless MC7430 card was used and /dev/cuaU0.2 is the only device where we get OK back.

Now, check if a SIM card is available and can be accessed:

cu -l /dev/cuaU0.2
Connected
AT+CPIN?
+CPIN: READY

There are multiple things that can go wrong here, the SIM card might not have been detected or you might have a pin on the SIM.

Once the SIM card is ready, quit cu with ~..

Step 2 - Configure Point to Point device

Go to Interfaces › Point-to-Point › Devices and click on Add in the upper right corner of the form.

Fill in the form like this (Example is for Dutch Mobile 4G KPN Subscription):

If you need to enter a PIN number, then click on Advanced Options

Click Save to apply the settings.

Step 3 - Assign the WAN interface

To assign the interface go to Interfaces › Assignments in our case we will make this our primary internet connection and change the WAN assignment accordingly.

To do so just change the Network port for WAN to ppp0 (/dev/cuaU0.0) - 4G Cellular Network.

Now click Save below the form.

If everything went fine, then you are all set, and the default gateway will be the one of you cellular connection.

Step 4 - Troubleshooting

In case it still does not work, first look at the log of the cellular device’s PPP connection, to do so go to: System › Log Files › General. If you are lucky you can see what went wrong directly in the log. Unfortunately, the PPP log is not very informative so it might not help at all.

If you can’t figure out what is wrong, then a reboot to reinitialize the device can sometimes help. This seems particularly true on embedded devices, better reboot once too much and if you got lost in the options, a factory reset to start from scratch is a good idea too. In our experience playing with SIM cards from different providers required factory resets (for whatever reason) to get them to work properly.

When the device seems to work properly then checkout if the interface was assigned an IP address, go to Interfaces › Overview and click on the WAN interface to see the details.

You should see an IP address, Gateway IP and ISP DNS server(s). If all is filled in, then either your firewall is blocking the traffic or the network connection is not working well.

In case you were not successful, you might have to check manually what is going on. Read the Troubleshooting PPP Connections section in the FreeBSD manual for more information and consult the Ixolate support forum.