As presented earlier, iptables uses the concept of separate rule tables for different packet processing functionality. Nondefault tables are specified by a command-line option. Three tables are available:
filter— The filter table is the default table. It contains the actual firewall filtering rules. The built-in chains include these:
nat— The nat table contains the rules for Source and Destination Address and Port Translation. These rules are functionally distinct from the firewall filter rules. The built-in chains include these:
mangle— The mangle table contains rules for setting specialized packet-routing flags. These flags are then ...