tldr/pages/linux/iptables.md

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 {{[-vnL --line-numbers|--verbose --numeric --list --line-numbers]}}

• Set chain policy rule:

sudo iptables {{[-P|--policy]}} {{chain}} {{rule}}

• Append rule to chain policy for IP:

sudo iptables {{[-A|--append]}} {{chain}} {{[-s|--source]}} {{ip}} {{[-j|--jump]}} {{rule}}

• Append rule to chain policy for IP considering protocol and port:

sudo iptables {{[-A|--append]}} {{chain}} {{[-s|--source]}} {{ip}} {{[-p|--protocol]}} {{tcp|udp|icmp|...}} --dport {{port}} {{[-j|--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 {{[-t|--table]}} {{nat}} {{[-A|--append]}} {{POSTROUTING}} {{[-s|--source]}} {{192.168.0.0/24}} {{[-j|--jump]}} {{MASQUERADE}}

• Delete chain rule:

sudo iptables {{[-D|--delete]}} {{chain}} {{rule_line_number}}