For the purposes of this chapter, you'll need to deploy a CentOS 7 and a Ubuntu 18.04 virtual machine. It is possible to use SUSE SLE 12 or openSUSE Leap instead of the CentOS and Ubuntu virtual machines. SUSE supports all options discussed in this chapter.
For the section about the Linux firewall, make sure that the firewalld software is installed and other firewall software is removed from the system to avoid conflicts. In RHEL/CentOS 7 based distributions, this is already the case. In Ubuntu, use the following commands:
sudo apt remove ufw
sudo apt install firewalld
In SUSE-based distributions, use the following commands:
sudo zypper install susefirewall2-to-firewalld
sudo susefirewall2-to-firewalld -c