All Types of Firewall in Networking – Detailed Explained

Types of Firewall

Firewalls are network security devices which is used to secure our network. Firewalls plays a vital role in network security. Today, technology grows very fast. Along with technology grow, the number of network attacks are also increased. Therefore, Network Security is the need for our business. In previous article we have already discussed some detailed information about Firewalls. But, in this article we will discuss various types of firewall based on their working.

Types of Firewall

In this article we will discuss some important types of firewall. We will discuss, Packet Filtering Firewalls, Stateful Inspection Firewalls, Circuit Level gateways, Application level gateways and Next Generation (NG) firewalls.

1. Packet Filtering  Firewall

Packet Filtering Firewall, As the name suggest, In Packet Filtering Firewalls, packet can be filter based on source or destinations internet protocol (IP) addresses, protocols and ports. Here, firewall is monitor each packet which is going to or coming from outside zone to inside zone and vice versa. The firewall inspects each IP packets and after the inspection, a decision will be made according to written polices on firewall. The IP packet might allowed or blocked depends upon written polices. But, everything will be happen after the packet inspection.

This types of firewall don’t know the states of any packet. Therefor, this firewall is called Stateless Packet Filtering.

2. Stateful Inspection Firewall

Stateful inspection, as the name suggests is a firewall technology, in which firewall maintain records of active connections. Thereafter, firewall will use this information to allow or block a IP packet. Simply, if firewall have packet stat in database, then only it allow the packet otherwise block the access.

Because, it allow or block dynamic packets, therefor, this types of firewall is called Dynamic Packet Filtering Firewall.

3. Circuit Level Gateways

Circuit Level Gateways, is a firewall technology, which works on Session Layer of OSI model. These firewalls use TCP handshaking to determine whether a IP packet is valid or invalid. Therefor, they identified whether a requested session is legitimate.

The main disadvantage of this firewall technology, is that it is not filter Individual Packets. Therefore, it might pass a malicious packet throw it. Today, we are using other firewalls than this types of firewall. Next Generation types of Firewall (described below) is widely used in industries.

4. Application Level Gateways

Application level Gateways (ALP), is a types of firewall or proxy firewall, which is used in network security. An Application Server (FTP, SIP, RTSP) are kept behind this firewall. We have to configure manual mapping of destination port and destination address on firewall. So, that if any one wants to access this server, he will never get the actual assigned IP and ports.

5. Next Generation Firewalls

I am confident you know about this types of firewall – Next Generation Firewalls (NGFW), is an advance firewall technology, which is a combination of traditional firewall with some advance network monitoring and filtering devices. The Next Generation Firewalls, can monitor and filter network traffic up-to 7th layer of OSI (Open System Interconnection) model. Next Generation firewalls have in-line Deep Packet Inspection (DPI) and Intrusion Prevention System/ Intrusion Prevention Detection(IPS/IDS).

Cisco Firepower, is an example of Next Generation Firewall.


In this articles, we discussed, about types of firewall. We mainly focus on different types of firewall like Packet Filtering Firewalls, Stateful Inspection Firewalls, Circuit Level gateways, Application level gateways and Next Generation (NG). We also discussed about Pros and Cons of different types of firewall.


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