6 examples for iptables

  # print out ip tables with verbose, numeric listings
iptables -vnL
        

  # Ban all IP addresses other than 123.123.123.123
iptables -P INPUT DROP
iptables -I INPUT -p tcp -s 123.123.123.123 -j ACCEPT
iptables -I OUTPUT -p tcp -d 123.123.123.123 -j ACCEPT
        

  # basics of iptables
# switch -A INPUT/OUTPUT
# switch -p tcp/udp
# switch -j ACCEPT/DROP
# destination port as --dport 80
        

  # Add a rule to the top of the INPUT chain to drop all incoming connections on all ports from the specified IP address
iptables -I INPUT 1 -s xxx.xxx.xxx.xxx -j DROP
        

  # Flush iptables until restart
iptables -F
        

  # switch -L : List all 
# switch -D : drop a defined rule
#// iptables -D INPUT 2 would drop the second rule in the list
#
# A valid input chain to allow all on port 80 would look like this:
# // iptables -A INPUT -p tcp --dport 80 -j ACCEPT
# this means all traffic on tcp port 80 is accepted
#
#
#
# lso I would recommend apt-get install iptables-persistent to help save and reload the rules automatically.