Save current iptables configuration:

service iptables save

List current iptables rules:

iptables -nL

Clear all iptables rules:

iptables -F

Drop all traffic(ban all incoming traffic):

iptables -A INPUT -j DROP

Open ports:

iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT   # allow ssh

Allow specify ip traffic in and out

iptables -A INPUT -p tcp -s [ip] -j ACCEPT
iptables -A OUTPUT -p tcp -d [ip] -j ACCEPT