This paper address a recent trend in network security. Firewalls are computer security systems that protect your office/home (PC) s or your network from intruders, hackers & malicious code. Firewalls protect you from offensive software that may come to reside on your systems or from prying hackers. In a day and age when online security concerns are the top priority of the computer users, Firewalls provide you with the necessary safety and protection. Deep Packet Inspection (DPI) is a form of computer network packet filtering that examines the data part of a packet as it passes an inspection point, searching for protocol non-compliance, viruses, spam, intrusions. Deep packet inspection (DPI) is normally referred to as a technology that allows packet-inspecting devices, such as firewalls and (IPS), to deeply analyze packet contents, including information from all seven layers of the OSI model. This analysis is also broader than common technologies because it combines techniques such as protocol anomaly detection and signature scanning, traditionally available in (IDS) and anti-virus solutions. firewall clustering explains firewall backup in the system for a unexpected crashes. clustering also will provide important benefit to the system, load balancing. Which will be divide the load and speed up the system. While clustering works in a synchronized manner availability of the also increases.