Changes

* The '''-I''' switch tells iptables to INSERT this line into the OUTPUT policy. This means it will be the first line in the policy. If we used a -A switch it would have appended the line and it would be the last line of the policy. If you are writing complex iptables where multiple matches can occur, it is important that the lines go in the right order. Most people simply write scripts to ensure this.* The '''-p''' tcp switch tells iptables to filter data by looking at TCP information in the packets. For now, we simply want to filter data by source and destination TCP ports so we need this switch.