Module 3

Module Overview

Title: Module 3: VLANs

Subject: Switching, Routing, and Wireless Essentials v7.0 (SRWE)

Module Objectives

Network Protocols Objective: Explain how network protocols enable devices to access local and remote network resources. The goal is to provide a comprehensive understanding of VLANs and their critical role in networking.

Topics Covered:

• Overview of VLANs

• VLANs in a Multi-Switched Environment

• VLAN Configuration

• VLAN Trunks

• Dynamic Trunking Protocol (DTP)

Overview of VLANs

VLAN Definitions: A VLAN, or Virtual Local Area Network, is a subnetwork that can segment networks logically, regardless of the physical location of the devices. VLANs enable easier management and grouping of devices with similar needs and characteristics:

• Segmentation of device groups on the same switches allows for improved data flow and device grouping.

• Improved organization and manageability: Network administrators can manage devices that share similar characteristics efficiently.

• Isolation of broadcasts, multicasts, and unicasts within VLANs limits unnecessary traffic, enhancing network efficiency.

• Each VLAN has a unique IP address range, allowing devices on separate VLANs to communicate without interference.

• Smaller broadcast domains lead to improved performance, as they minimize the amount of broadcast traffic in the network.

Benefits of VLAN Design

• Smaller Broadcast Domains: Reduces broadcast traffic which can bog down network performance.

• Improved Security: Communication is restricted to users within the same VLAN, minimizing the risk of eavesdropping and attacks.

• Improved IT Efficiency: Groups devices by specific needs, making it easier to manage application traffic.

• Reduced Cost: One switch can handle multiple VLANs, reducing the need for additional hardware.

• Better Performance: Less traffic overall leads to better bandwidth utilization as there is less contention for resources among users.

• Simpler Management: Similar resource needs across grouped devices simplify administrative tasks involved in network management.

Types of VLANs

1. Default VLAN:

   • VLAN 1 - Cannot be deleted or renamed; serves as the default for management and native VLAN.

2. Data VLAN:

   • Handles user-generated traffic, such as emails, web traffic, and file transfers.

3. Native VLAN:

   • Used for trunk links; non-tagged frames are assigned to this VLAN, facilitating communication with devices that do not support VLAN tagging.

4. Management VLAN:

   • Only carries management traffic such as SSH or Telnet, separating management from user traffic for security.

5. Voice VLAN:

   • Dedicated to Voice over IP (VoIP) traffic, requiring high Quality of Service (QoS) and low latency to maintain call quality.

Packet Tracer Activity

Objective: Observe broadcast traffic in a VLAN implementation through hands-on simulation to reinforce learning points.

VLANs in a Multi-Switched Environment

Defining VLAN Trunks:

• Definition of a Trunk: A trunk is a link that carries multiple VLAN traffic, enabling VLANs to extend across the network.

• VLAN trunks automatically support all VLANs using 802.1Q trunking.

Networks Without and With VLANs

• Without VLANs: All network traffic is received by all devices irrespective of their data needs, leading to potential data bottlenecks.

• With VLANs: Traffic is confined to specific VLANs; communication between VLANs requires Layer 3 devices (e.g., routers or Layer 3 switches) to ensure proper routing.

VLAN Tagging

IEEE 802.1Q Header:

• Comprises 4 Bytes, which include:

  • Tag Protocol ID (TPID): Identifies the frame as a tagged frame, represented in hexadecimal as 0x8100.

  • User Priority and VLAN ID (VID): Identifies the specific VLAN the traffic belongs to.

Native VLANs and 802.1Q Tagging

• Tagging Basics: All VLANs become tagged, with a designated native VLAN to handle untagged traffic seamlessly.

• Configuration consistency is crucial across trunk links to prevent connectivity issues.

Voice VLAN Tagging

• VoIP phones require specific tagging and service capabilities, such as Class of Service (CoS), to prioritize voice traffic effectively.

Verification of VLAN Information

• Use commands like show interfaces and show vlan to verify VLAN assignments and configurations.

Packet Tracer Activity

• Engage with simulation activities to deepen understanding of VLAN implementations.

VLAN Configuration

VLAN Ranges on Catalyst Switches

• Normal Range: VLANs 1-1005

• Extended Range: VLANs 1006-4095

• Characteristics: VLAN details are stored in the vlan.dat file; support for extended ranges might depend on the switch model.

VLAN Creation Commands

• Commands for creating and naming VLANs must be executed in global configuration mode, enhancing the organization of device management.

VLAN Port Assignment Commands

• Assign VLANs to interface ports using specific commands to tailor traffic management for each port.

Data and Voice VLAN Setup

• Access ports are assigned to one data VLAN and can connect to one Voice VLAN concurrently to support different types of traffic effectively.

Verify VLAN Information

• Utilize show vlan commands to gather details about the VLAN configurations and assigned ports.

Change and Delete VLANs

• Specific procedures are in place for modifying and removing VLANs, including essential precautions to avoid network disruptions.

Packet Tracer Activity

• Configure VLANs through simulation exercises to practically apply learned concepts.

VLAN Trunks

Trunk Configuration Commands

• Commands specifically designed for configuring VLAN trunks on switches for multi-VLAN operations.

Trunk Configuration Example

• Example commands provide practical illustrations of how to set up VLAN trunks effectively.

Verifying and Resetting Trunk Configuration

• Procedures are essential for verifying current trunk settings and restoring defaults when necessary.

Packet Tracer Activities

• Tasks designed to focus on configuring and verifying VLAN trunks through simulation to reinforce knowledge.

Dynamic Trunking Protocol (DTP)

Introduction to DTP

• DTP is a Cisco proprietary protocol designed for negotiating trunk links automatically, streamlining network configuration.

Negotiated Interface Modes

• Various options exist for configuring switch interfaces via DTP, affecting how trunk links are established.

DTP Configuration Results

• Outcomes vary based on how DTP settings are configured on switches, influencing overall network behavior.

Verification of DTP Mode

• Use show dtp interface to check current configurations and operational states of DTP.

Packet Tracer Activity

• Configure and verify DTP settings in a controlled simulation to understand how DTP impacts trunk negotiations.

Conclusion: Key Points Learned

• VLANs create logical networks that enhance segmentation and improve management of broadcast domains.

• Trunks enable the carrying of multiple VLAN traffic using tagging methods (802.1q).

• Voice VLANs are specifically designated for VoIP, ensuring high prioritization and quality of service requirements.

• Dynamic Trunking Protocol (DTP) helps facilitate dynamic trunk negotiations between switches, increasing network adaptability.

New Terms and Commands

• VLAN: Virtual Local Area Network

• Data VLAN: Handles user traffic

• Native VLAN: Used for untagged traffic on trunk links

• Management VLAN: Used for network management tasks

• Voice VLAN: Optimized for VoIP traffic

• Commands: show vlan brief, vlan vlan-id, switchport mode access, switchport trunk allowed vlan, show interfaces switchport.

Additional Notes: VLANs play a crucial role in modern networks by enhancing efficiency, security, and management. Understanding their deployment and configuration is fundamental to optimizing network performance.