How to Configure iptables Firewall Rules

iptables is the traditional Linux firewall. While UFW and firewalld are easier, understanding iptables gives you fine-grained control.

View Current Rules

iptables -L -n -v

Basic Rules

# Allow established connections
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow SSH
iptables -A INPUT -p tcp --dport 22 -j ACCEPT

# Allow HTTP/HTTPS
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j ACCEPT

# Allow loopback
iptables -A INPUT -i lo -j ACCEPT

# Drop everything else
iptables -A INPUT -j DROP

Save Rules

# Ubuntu/Debian
apt install iptables-persistent -y
netfilter-persistent save

# RHEL-based
service iptables save

Delete a Rule

iptables -L --line-numbers
iptables -D INPUT 3  # Delete rule number 3