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Logical Security: The Network Layer

• A local area network (LAN) is comprised of servers, computers, peripheral devices, and network
components, all of which are located in the same physical location.
• A LAN enables various devices to share resources.
• A router is used to connect one or more LANs together so that resources can be shared across
LANs.
• When an organization has multiple locations in a small office park, a campus area network (CAN)
is used to connect the LANs between buildings.
• Similarly, a metropolitan area network (MAN) is used to connect networks within a city, and a
wide area network (WAN) is deployed to connect multiple LAN’s all over the world.

DMZ

The demilitarized zone (DMZ) is:

• A logical or physical subnetwork that separates the internal network (LANs) from external untrusted
networks.
• Commonly referred to as the perimeter network or a screened subnetwork.
• Considered a buffer area where the outward-facing network infrastructure and services reside. Examples
include web servers, email gateways, FTP servers, etc.
• Provides an additional layer of security by requiring traffic to pass through two firewalls.
• Separates the internal private network from the external network.

Network Devices

Repeater
• Receives digital signals, and then passes them along to the next network segment.
• May amplify (or strengthen) the signal, especially in wireless networks.

Switches
• Historically hubs, serve as the central connection for network connectivity.
• Where data enters and broadcasts to other parts of the network.
• Receives and forwards incoming data signals.
• Devices are plugged into switches in wired networks.

Routers
• Similar to switches but usually reside between networks or network segments .
• Historically used as bridges that connect two or more LANs.

AD

Domain Controller
• A domain controller is a Windows server that has Active Directory Domain Services (AD DS)
installed.
• A domain controller is used for network security authentication requests.

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