<p>Although there is more abstract software to manage firewalls, like <em>ufw</em> on debian-based systems and <em>firewall-cmd</em> on redhat systems, Iptables will help you understand what actually happens during filtering, mangling or routing a package. <a href="https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html">https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html</a> has a structured approach in explaining <u>what happends when a package hits the firewall</u>. Pay extra attention to Network Address Translation. Here is another nice HOWTO: <a href="https://netfilter.org/documentation/HOWTO/NAT-HOWTO-5.html">https://netfilter.org/documentation/HOWTO/NAT-HOWTO-5.html</a>
</p>
<h2><a name="section_1_2">Virtual Private Networks and Tunneling</a></h2>
<p>Although there is more abstract software to manage firewalls, like <em>ufw</em> on debian-based systems and <em>firewall-cmd</em> on redhat systems, Iptables will help you understand what actually happens during filtering, mangling or routing a package. <a href="https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html">https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html</a> has a structured approach in explaining <u>what happends when a package hits the firewall</u>. Pay extra attention to Network Address Translation. Here is another nice HOWTO: <a href="https://netfilter.org/documentation/HOWTO/NAT-HOWTO-5.html">https://netfilter.org/documentation/HOWTO/NAT-HOWTO-5.html</a>
</p>
<h2><a name="section_1_2">Virtual Private Networks and Tunneling</a></h2>