iptables_quick_setup.txt

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -m comment --comment "allow established sessions to receive traffic"
iptables -I INPUT -p tcp --dport 1723 -j ACCEPT -m comment --comment "allow PPTPD"
iptables -I INPUT -p tcp --dport 22 -j ACCEPT -m comment --comment "allow SSH"
iptables -I INPUT -p gre -j ACCEPT -m comment --comment "allow GRE protocol"
iptables -A INPUT -p icmp --icmp-type 0 -m state --state ESTABLISHED,RELATED -j ACCEPT -m comment --comment "allow icmp"
iptables -A INPUT -i lo -j ACCEPT -m comment --comment "allow loopback"
iptables -A INPUT -j DROP -m comment --comment "block everything else"
iptables -t nat -I POSTROUTING -o eth0 -j MASQUERADE -m comment --comment "masquerade network on eth0"

#save to file all the rules
iptables-save > /etc/iptables.rule
# then edit and add this to /etc/rc.local to run it at startup
iptables-restore < /etc/iptables.rules