3. iptables: The Legacy Linux Firewall Administration Program
Chapter 2, “Packet-Filtering Concepts,” covered the background ideas and concepts behind a packet-filtering firewall. Each built-in list of rules, sometimes called a rule chain, has its own default policy. Each rule can apply not only to an individual chain, but also to a specific network interface, message protocol type (such as TCP, UDP, or ICMP), and service port or ICMP message type number. Individual acceptance, denial, and rejection rules are defined for the INPUT chain and the OUTPUT chain, as well as for the FORWARD chain, which you’ll learn about at the end of this chapter and in Chapter 7, “Packet Forwarding.”
This chapter covers the iptables firewall administration program ...
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