First, let's look at the high availability scenario topology shown in the following diagram:

Figure 17.1 – A high availability topology example

In the preceding diagram, we have two OPNsense firewalls connected using a dedicated network interface. This interface, which we will call the HA Interface, is the network interface that will keep the firewall states synchronized using the pfsync protocol. We also use it to run XMLRPC to sync OPNsense 1's (master node) configuration to OPNsense 2 (backup node).

Proposed scenario

You can quickly reproduce this scenario using VirtualBox while configuring the network and the virtual machines using the steps we learned about in the previous chapters of this book (modifying the steps according to your lab environment).

First, configure two OPNsense firewalls, add a network interface (both from OPNsense), and connect them directly using a network interface that we will...