VLANs Overview and Basic Requirements

What is VLAN?

A Virtual Local Area Network (VLAN) is a logically segmented network within a switch, allowing devices to communicate as if they are on the same physical network. VLANs enhance network security, improve performance, and simplify management by isolating traffic.

What is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a network protocol that dynamically assigns IP addresses to devices on a network. This reduces manual configuration efforts and ensures efficient IP address management.

Types of DHCP Allocations:

1. Dynamic Allocation - Automatically assigns IP addresses for a set lease time.
2. Static Allocation - Assigns a predefined IP address to a specific device based on its MAC address.
3. Automatic Allocation - Permanently assigns an IP address to a device the first time it connects.

What is an Access Control List (ACL)?

An Access Control List (ACL) is a set of rules that control incoming and outgoing network traffic based on defined security policies.

Types of ACLs:

1. Standard ACLs - Filter traffic based only on source IP addresses.
2. Extended ACLs - Filter traffic based on source/destination IP, port numbers, and protocols.
3. Named ACLs - Allow custom-named ACLs for better organization and management.

ACLs help secure VLANs by restricting unauthorized communication between network segments.

VLAN Basic Requirements

1. Network Devices:

   • Layer 2 and Layer 3 switches
   • Routers (for inter-VLAN routing)
   • PCs or other end devices

2. Key Configurations:

   • VLAN creation on switches
   • Assigning VLANs to switch ports
   • Configuring trunk ports for inter-switch communication
   • Setting up inter-VLAN routing (if needed)
   • Implementing DHCP for dynamic IP allocation
   • Applying Access Control Lists (ACLs) for security

Summary of VLAN Implementations

• Simple VLAN Configuration:

  • Layer 3 switch connects multiple VLANs
  • PCs are grouped based on departments (e.g., HR, IT, Finance, Interns)

• VLAN with ACLs and DHCP:

  • Router assigns dynamic IPs
  • ACLs restrict unauthorized VLAN communication

• Layer 2 VLAN-only Setup:

  • Only same VLAN devices can communicate
  • Switches are interconnected using trunk ports

VLANs help in better network segmentation, control, and performance optimization, making them essential for efficient enterprise networking.