What screened subnet Architecture?

Let’s take a look at how a typical Screened Subnet Architecture is setup:

From this diagram, note that there are two, not one, firewalls in the network structure.The exterior firewall is configured to allow external traffic to access the subnet section (Perimeter Network) where you have put the public service hosts (Bastion Hosts) such as your e-mail server, web server, and/or DNS server, for example. The Screened Subnet is  also called “DM Zone”  (demilitarized zone) or simply “DMZ”.The internal firewall acts a second gatekeeper to keep external visitors from directly coming into your internal corporate network.The subnet section where you have put the service hosts is called “Screened Subnet” or “Perimeter Network,” hence the name “Screened Subnet Architecture” has become used for this type of network architecture.