Quick how to for my personal records. iptables is an open source firewall (and it does a lot more) included with most linux distributions.

Steps to add new rule to existing configuration

• Check the list of rules and their corresponding sequence

sudo iptables -vL –line-numbers

• Add the new rule at the required location/sequence

sudo iptables -I INPUT LINE_NUMBER RULE

Example :

iptables -I INPUT 8 -s X.X.X.X/24 -p tcp -m state –state NEW -m tcp –dport 3128 -j ACCEPT

• Save the configuration

sudo serivce iptables save

Thx to Sijis for helping with the commands.