There are several types of firewalls that work on different layers of the OSI model. Depending on the kind of service and security you need for your network, you need to choose the right type of firewall. The following are the list of seven different types  firewalls that are widely used for network security.

• Screened host firewalls
• Screened subnet firewalls
• Packet filter firewalls
• Stateful inspection firewalls
• Hybrid firewalls
• Proxy server firewalls
• Application level (gateway) firewalls

Screened host firewalls:

There are two types of screened host-one is single homed bastion host and the other one is dual homed bastion host. In case of single homed bastion host the firewall system consists of a packet filtering router and a bastion host. A bastion host is basically a single computer with high security configuration, which has the following characteristics:

• Traffic from the Internet can only reach the bastion host; they cannot reach the internal network.
• Traffic having the IP address of the bastion host can only go to the Internet. No traffic from the internal network can go to the Internet.

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