iptables

List rules with line numbers Show INPUT chain rules with packet/byte counters iptables -L INPUT --line-numbers -n -v #iptables#linux#network#security Allow incoming port Append a rule to accept inbound HTTPS traffic iptables -A INPUT -p tcp --dport 443 -j ACCEPT #iptables#linux#network#security Block IP address Insert DROP rule at position 1 for a specific source IP iptables -I INPUT 1 -s 203.0.113.5 -j DROP #iptables#linux#network#security NAT: masquerade outbound Enable IP masquerading for outbound traffic (router/NAT) iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE #iptables#linux#network Save and restore rules Persist rules across reboots iptables-save > /etc/iptables/rules.v4 iptables-restore < /etc/iptables/rules.v4 #iptables#linux#network Delete a rule by number Remove rule number 3 from the INPUT chain iptables -D INPUT 3 #iptables#linux#network Rate-limit connections Allow max 3 new SSH connections per minute iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m limit --limit 3/min --limit-burst 5 -j ACCEPT #iptables#linux#network#security nftables: list all rules Show complete nftables configuration nft list ruleset #iptables#linux#network#security nftables: add accept rule Accept inbound TCP traffic on port 8080 in nftables nft add rule inet filter input tcp dport 8080 accept #iptables#linux#network#security nftables: flush all rules Delete all nftables rules (caution: drops all firewall rules) nft flush ruleset #iptables#linux#network#security