Lecture Notes: Virtual Local Area Network (VLAN)

Introduction to VLAN

• Scenario: Need for five LANs, typically requiring five switches.
• Solution: VLANs allow creation of multiple local area networks (LANs) within a single switch.

Learning Outcomes

1. Understanding the need for VLANs.
2. Comprehending the working mechanism of VLANs.
3. Recognizing the benefits of VLANs.
4. Identifying the types of VLANs.
5. Understanding VLAN frame tagging.

What is VLAN?

• Concept: Logical partitioning of a switch to create multiple LANs within a single switch without physical partitioning.
• Analogy: Breaking a switch into parts logically, not physically.
• VLANs allow devices connected to different ports to act as separate LANs.

Working of VLANs

• Example: Creation of three VLANs (Yellow, Blue, Green) with distinct IP addressing schemes.
• Communication: Only devices within the same VLAN can communicate directly.
• Broadcast: Messages are only received within the same VLAN.
• Inter-VLAN Communication: Requires a router to connect different VLANs.

Theoretical Aspects of VLAN

• VLAN as a Broadcast Domain: Each VLAN is a separate broadcast domain with its own IP network.
• Isolation: VLANs are mutually isolated; communication requires a router.
• Host Awareness: Hosts are unaware of their VLAN membership; only the switch knows.

Benefits of VLANs

• Security: Isolation of broadcast domains enhances security.
• Cost Reduction: Fewer switches required; logical partitioning reduces hardware costs.
• Performance: Improved performance and switch utilization.
• Efficiency: Enhanced IT staff efficiency and simplified management.

Types of VLANs

1. Data VLAN
2. Default VLAN
3. Native VLAN
4. Management VLAN
5. Voice VLAN

VLAN Frame Tagging

• Ethernet Frame Structure:
  • Destination MAC Address
  • Source MAC Address
  • Type/Length
  • Data
  • Frame Check Sequence
• Tagging: Added between source MAC and type field.
  • Ethernet Type: 2 bytes
  • Priority
  • VLAN Identifier: 12 bits
• Purpose: Identifies VLAN membership for frames traveling over trunk links.

Frame Tagging Protocol

• IEEE 802.1Q: Popular VLAN tagging protocol.
  • Function: Structures tagging header added to frames.
  • Switch Role: Tags frames for trunk links, removes tags for non-trunk ports.
  • Flexibility: Tagged frames can traverse multiple switches and reach the correct VLAN destination.

Conclusion

• Recap of Outcomes:
  • Importance of VLANs.
  • How VLANs function and their benefits.
  • Understanding VLAN types and frame tagging.
• End Note: Emphasis on the power and efficiency of VLAN technology.