• Back-to-back configuration: This configuration has the perimeter
network situated between two firewall devices, which could be black
box appliances or Microsoft Internet Security and Acceleration (ISA)
Servers
• 3-leg perimeter configuration: In this scenario, the perimeter network is
usually attached to a separate connection of the company firewall.
Therefore, the firewall has three connections—one to the company
LAN, one to the perimeter network, and one to the Internet