How to configure the 3G/LTE Interface on the ZyWALL/USG as a WAN Backup?

This is an example of using ZyWALL/USG to configure the 3G/LTE interface as a WAN backup that ensures the ZyWALL/USG provides internet connections continuously when the primary WAN interface is down. After configuration, it can provide additional mobile broadband WAN connectivity or a redundant link for maximum reliability.

Set Up the 3G/LTE Interface on the ZyWALL/USG
1. Connect a compatible mobile broadband USB device to use a cellular connection.
2. On the ZyWALL/USG, the connected device will automatically display in the Cellular Interface Summary. Click "Activate" and then the "Apply" button at the bottom of this page.

Configuration > Network > Interface > Cellular > Activate

3. The default Connectivity method is Nailed-Up. The connection should always be up after you activate the cellular interface. You can click "Edit" and go to the Connectivity section to clear the Nailed-Up check box to have the ZyWALL/USG establish the connection only when there is traffic.

Configuration > Network > Interface > Cellular > Connect

Configuration > Network > Interface > Cellular > Edit

Set Up the Trunk on the ZyWALL/USG

1. On the ZyWALL/USG configure a name for you to identify the Trunk profile and set the Load Balancing Algorithm field to be Weighted Round Robin.
Add wan1 and enter 3 in the Weight column. Add wan2 and enter 2 in the Weight column. Add cellular1, change Mode to be the Passive mode, enter 1 in the Weight column. Click OK to return to the configuration screen.

Configuration > Network > Interface > Trunk > User Configuration > Add Trunk

2. In the configuration screen, go to the default WAN Trunk section, select User Configured Trunk and select the newly created Trunk from the list box. Click Apply.

Configuration > Network > Interface > Trunk > Default WAN Trunk > User Configured Trunk

1. Check the Interface Statistics when wan1 and wan2 connections are up. You can see both wan1 and wan2 Status are up, Tx B/s displays the transmission speed and Rx B/s displays the reception speed; cellular1 Status is connected but there is no traffic going through this interface.

Monitor > Interface Status > Interface Statistics

2. After disconnecting both wan1 and wan2, you can see both wan1 and wan2 Status are Down and no traffic goes through these two interfaces. The backup cellular1 Status is connected and all the traffic is going through this interface.

Monitor > Interface Status > Interface Statistics

What Can Go Wrong?
If there is no traffic going through the cellular interface when other interfaces are down, please make sure you have a compatible mobile broadband device installed or connected. Also, make sure the cellular interface is enabled and the cellular interface has the correct user name, password, and PIN code configured with the correct casing.

PLEASE NOTE: In case you can not find a compatible dongle!

You can use a LTE router instead which you can connect to an external WAN interface of your firewall.

You can use a NR7101 in bridge mode which can be installed outdoor. This might result in better LTE reception than using a dongle in your server rack.