Native firewall in Linux and security in general is done by two components:

• Firewall: Iptables for old linux and firewalld for new ones
• Selinux: The most annoying form of security, which blocks everything

So we have to control both in order to maintain our connections and to determine who is allowed in and out.

That is done mainly with the firewall by allowing / blocking ports. Let's see how it is done.

Firewalld is the newer version of the iptables and allows port forwarding and