Firewall is used to protect local network from outside untrusted public network or Internet. Every packet coming to and going out from network is inspected at firewall. Local network policies are converted into rules and stored in firewall. It is used to restrict access of the external network into local network and vice versa. Packets are checked against the rules serially. Therefore, increase in the number of rules decreases the firewall performance. The key thing in performance improvement is to reduce number of firewall rules.