iptables

@firewalls

Set up default DROP rule for eth0


iptables -P INPUT DROP

Allow existing connections to continue


iptables -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT

Accept everything from the 192.168.1.x network


iptables -A INPUT -i eth0 -s 192.168.1.0/24 -j ACCEPT

Drop a single host


iptables -I INPUT -s 192.168.1.100 -j DROP

Allow connections from this host to 192.168.2.10


::

iptables -A OUTPUT -o eth0 -d 192.168.2.10 -j ACCEPT

Flush table


::

iptables --flush

Allow incoming HTTP


::

iptables -A INPUT -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT

Limit connections


::

iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT

Simple IP masquerading


::

echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o $EXT_IFACE -j MASQUERADE

Backup, reload iptables rules


::

iptables-save > ./file
iptables-restore < ./file

File location


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/etc/sysconfig/iptables