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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.