Local Area Network (LAN) and VLANs

Definition of LAN

• A Local Area Network (LAN) is a group of devices within the same broadcast domain.
• Example setup:
  • Two switches: Red switch and Blue switch.
  • Devices on the Red network are in one broadcast domain.
  • Devices on the Blue switch are in a separate broadcast domain.
  • Used for security and to limit broadcasts.

Inefficiencies in Traditional LANs

• Requires multiple separate switches.
• Increased cost and effort in maintenance (power, configuration, management).
• Underutilization of switch interfaces due to buying more switch capacity than needed.

Virtual LAN (VLAN)

• VLAN Concept: Logical grouping of devices in the same broadcast domain across a single physical switch.
• Benefits:
  • Reduces need for multiple switches.
  • Offers same functionality in a cost-effective manner.
  • Manages network separation logically rather than physically.

VLAN Implementation

• Can have multiple VLANs on a single switch (e.g., Red, Blue, Green networks).
• Assigns specific ports on a switch to different VLANs:
  • Port 1: Red network (VLAN 1)
  • Port 9: Blue network (VLAN 2)
  • Port 17: Green network (VLAN 3)
• Reduces costs by using a single switch for multiple networks.

Virtual Private Network (VPN)

Definition and Purpose

• VPN: A technology to securely send information over a public network (internet).
• Encrypts data to secure it from unauthorized access during transmission.

VPN Components

• VPN Client: Software on a user device to connect to a VPN.
• VPN Concentrator: Device that manages VPN connections, either standalone or integrated into another device like a firewall.
• Encryption/Decryption Process:
  • Data sent by the client is encrypted.
  • VPN concentrator decrypts incoming data and forwards it to the corporate network.
  • Outgoing data from the network is encrypted by the concentrator before being sent to the client.

VPN Usage

• Common in modern operating systems.
• Ensures security on open networks (e.g., public Wi-Fi).
• Provides an encrypted tunnel for data between client and concentrator.
• Can be always-on or enabled manually by the user.
• Automatic behind-the-scenes operation once activated.