Final answer:
A perimeter network that is connected to a firewall and functions separately from the LAN is known as a Demilitarized Zone (DMZ).
Step-by-step explanation:
The type of network you are referring to is commonly known as a Demilitarized Zone (DMZ). This type of network acts as a buffer zone between the public internet and the local area network (LAN). It adds an additional layer of security, allowing external users limited access to certain services without exposing the entire network. Usually, servers that need to be accessible to both internal and external users, such as web servers, email servers, and DNS servers, are placed in the DMZ. The firewall is configured to control the traffic between the internet, the DMZ, and the LAN, ensuring that unauthorised access is blocked.