SOA Servers Configuration and DMZ

 DMZ or demilitarized zone (sometimes referred to as a perimeter network) is a physical or logical subnetwork that contains and exposes an organization's external-facing services to a larger and untrusted network, usually the Internet. The purpose of a DMZ is to add an additional layer of security to an organization's local area network (LAN); an external network node only has direct access to equipment in the DMZ, rather than any other part of the network.

There are many different ways to design a network with a DMZ. Two of the most basic methods are with a single firewall, also known as the three legged model, and with dual firewalls. These architectures can be expanded to create very complex architectures depending on the network requirements.

Single firewall[edit]

Diagram of a typical three-legged network model employing a DMZ using a single firewall.

A single firewall with at least 3 network interfaces can be used to create a network architecture containing a DMZ. The external network is formed from the ISP to the firewall on the first network interface, the internal network is formed from the second network interface, and the DMZ is formed from the third network interface. The firewall becomes a single point of failure for the network and must be able to handle all of the traffic going to the DMZ as well as the internal network. The zones are usually marked with colors -for example, purple for LAN, green for DMZ, red for Internet (with often another color used for wireless zones).

Dual firewall[edit]

Diagram of a typical network employing DMZ using dual firewalls.

The most secure approach, according to Stuart Jacobs,^[1] is to use two firewalls to create a DMZ. The first firewall (also called the "front-end" or "perimeter"^[2] firewall) must be configured to allow traffic destined to the DMZ only. The second firewall (also called "back-end" or "internal" firewall) only allows traffic from the DMZ to the internal network.

This setup is considered^[1] more secure since two devices would need to be compromised. There is even more protection if the two firewalls are provided by two different vendors, because it makes it less likely that both devices suffer from the same security vulnerabilities. For example, accidental misconfiguration^{[dubious – discuss]} is less likely to occur the same way across the configuration interfaces of two different vendors, and a security hole found to exist in one vendor's system is less likely to occur in the other one. One of the drawbacks of this architecture is that it's more costly, both to purchase, and to manage.^[3] The practice of using different firewalls from different vendors is sometimes described as a component of a "defense in depth"^[4]security strategy.