All Types of Firewall in Networking – Detailed Explained

Types of Firewall

Firewalls are network security devices which are used to secure our network. Firewalls play a vital role in network security. Today, technology grows very fast. Along with technology grow, the number of network attacks is also increased. Therefore, Network Security is the need for our business. In the previous article, we have already discussed some detailed information about Firewalls. But, in this article, we will discuss various types of a 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, suggests In Packet Filtering Firewalls, a packet can be filter based on source or destinations internet protocol (IP) addresses, protocols, and ports. Here, the 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 policies on the firewall. The IP packet might be allowed or blocked depends upon written polices. But, everything will happen after the packet inspection.

This types of firewall don’t know the states of any packet. Therefore, 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, the firewall will use this information to allow or block an IP packet. Simply, if the firewall has packet stat in the database, then only it allow the packet otherwise block the access.

Because it allows or blocks dynamic packets, therefore, these types of firewall are 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 an IP packet is valid or invalid. Therefore, they identified whether a requested session is legitimate.

The main disadvantage of this firewall technology is that it is not filtered Individual Packets. Therefore, it might pass a malicious packet throw it. Today, we are using other firewalls than these 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 type 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 the manual mapping of the destination port and destination address on the firewall. So, that if anyone 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 the firewall – Next-Generation Firewalls (NGFW), is an advanced firewall technology, which is a combination of the 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 a Next-Generation Firewall.


In this article, 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 the Pros and Cons of different types of firewall.


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