iptables

Configure tables, chains and rules of the Linux kernel IPv4 firewall. Use ip6tables to set rules for IPv6 traffic. See also: iptables-save, iptables-restore. More information: https://manned.org/iptables.

• View chains, rules, packet/byte counters and line numbers for the filter table:
  sudo iptables --verbose --numeric --list --line-numbers
• Set chain [P]olicy rule:
  sudo iptables --policy {{chain}} {{rule}}
• [A]ppend rule to chain policy for IP:
  sudo iptables --append {{chain}} --source {{ip}} --jump {{rule}}
• [A]ppend rule to chain policy for IP considering [p]rotocol and port:
  sudo iptables --append {{chain}} --source {{ip}} --protocol {{tcp|udp|icmp|...}} --dport {{port}} --jump {{rule}}
• Add a NAT rule to translate all traffic from the 192.168.0.0/24 subnet to the host's public IP:
  sudo iptables --table {{nat}} --append {{POSTROUTING}} --source {{192.168.0.0/24}} --jump {{MASQUERADE}}
• [D]elete chain rule:
  sudo iptables --delete {{chain}} {{rule_line_number}}