跨越兩個VLAN的通訊 | 配置Router on Stick | CCNA實用 | CCNA 200-301 |

Table of Contents

1. 📚 Introduction
2. 🌐 Understanding VLANs
   • 📌 What is a VLAN?
   • 📌 Benefits of Using VLANs
   • 📌 Types of VLANs
3. 📡 VLAN Configuration on Switches
   • 📌 Creating VLANs on Switches
   • 📌 Adding Ports to VLANs
   • 📌 Trunk Ports Configuration
4. 🖧 Inter-VLAN Routing
   • 📌 Introduction to Inter-VLAN Routing
   • 📌 Configuring Router on a Stick
   • 📌 Configuring Subinterfaces
   • 📌 Testing Inter-VLAN Communication
5. 💡 Pros and Cons of Using Inter-VLAN Routing
   • 📌 Pros of Inter-VLAN Routing
   • 📌 Cons of Inter-VLAN Routing
6. ❓ Frequently Asked Questions (FAQs)
   • 📌 How do VLANs improve network performance?
   • 📌 Can I have multiple VLANs on a single switch?
   • 📌 What is the purpose of a trunk port?
   • 📌 Are there any limitations of router on a stick?
7. 🔗 Resources

Introduction

In today's discussion, we will explore the concept of VLANs (Virtual Local Area Networks) and learn how to establish communication between different VLANs using inter-VLAN routing. VLANs are an essential component of network segmentation and can greatly enhance network performance and security. We will also delve into the configuration of VLANs on switches and the process of configuring a router on a stick to enable inter-VLAN communication. So let's dive in and unravel the mysteries of VLANs and inter-VLAN routing!

Understanding VLANs

What is a VLAN?

Virtual Local Area Networks (VLANs) are a logical segmentation of a physical network into multiple virtual networks. Each VLAN operates as a separate broadcast domain, allowing for efficient network management and improved security. By grouping devices together based on their shared requirements or functions, VLANs enable network administrators to streamline network traffic and enhance overall performance.

Benefits of Using VLANs

The use of VLANs offers several advantages for network management and security. Some key benefits include:

• Improved network performance: By segmenting network traffic, VLANs reduce collision domains and enhance overall network performance.
• Enhanced network security: VLANs provide a layer of security by isolating sensitive data and preventing unauthorized access between VLANs.
• Simplified network administration: Network administrators can easily manage VLANs, as they allow for logical grouping and efficient configuration of network resources.
• Increased flexibility: VLANs enable network administrators to easily reconfigure the network without physically relocating devices or rewiring connections.

Types of VLANs

There are different types of VLANs that can be implemented based on specific network requirements. The most common types include:

• Default VLAN (VLAN 1): This is the initial VLAN that is created by default on network devices. All switch ports are a member of VLAN 1 unless explicitly assigned to another VLAN.
• Data VLAN: These VLANs are used to segment user data traffic, such as internet browsing, file sharing, and general communication.
• Management VLAN: This VLAN is dedicated to network management tasks and allows administrators to access and configure network devices remotely.
• Voice VLAN: Designed specifically for Voice-over-IP (VoIP) applications, this VLAN prioritizes voice traffic to ensure high-quality communication.
• Native VLAN: The native VLAN is used for untagged traffic and is typically assigned to a specific VLAN to handle untagged frames received on a trunk port.

VLAN Configuration on Switches

Creating VLANs on Switches

To configure VLANs on switches, follow these steps:

1. Enter the configuration mode on the switch by typing configure terminal.
2. Define the VLAN by typing vlan [vlan_id]. Replace [vlan_id] with the desired VLAN number.
3. Assign a name to the VLAN using the name [vlan_name] command. Replace [vlan_name] with the desired name.
4. Repeat steps 2 and 3 for each VLAN that needs to be created.
5. Exit configuration mode by typing exit or pressing Ctrl+Z.
6. Verify the VLAN configuration using the show vlan brief command.

Adding Ports to VLANs

To add switch ports to VLANs, follow these steps:

1. Enter the configuration mode on the switch by typing configure terminal.
2. Select the interface or range of interfaces using the interface range [interface_range] command. Replace [interface_range] with the desired interface range.
3. Assign the selected interfaces to the desired VLAN using the switchport access vlan [vlan_id] command. Replace [vlan_id] with the VLAN number.
4. Repeat steps 2 and 3 for each interface or range of interfaces that needs to be assigned to a VLAN.
5. Exit configuration mode by typing exit or pressing Ctrl+Z.
6. Verify the port membership using the show vlan brief command.

Trunk Ports Configuration

To configure trunk ports for inter-VLAN communication, follow these steps:

1. Enter the configuration mode on the switch by typing configure terminal.
2. Select the interface or range of interfaces using the interface range [interface_range] command. Replace [interface_range] with the desired interface range.
3. Configure the selected interfaces as trunk ports using the switchport mode trunk command.
4. Optionally, allow specific VLANs on the trunk using the switchport trunk allowed vlan [vlan_list] command. Replace [vlan_list] with the VLAN IDs to allow on the trunk.
5. Repeat steps 2 to 4 for each interface or range of interfaces that needs to be configured as trunk ports.
6. Exit configuration mode by typing exit or pressing Ctrl+Z.
7. Verify the trunk port configuration using the show interface trunk command.

Inter-VLAN Routing

Introduction to Inter-VLAN Routing

Inter-VLAN routing is the process of enabling communication between different VLANs. By leveraging a router, we can route traffic between VLANs and establish connectivity. One common method for inter-VLAN routing is using a technique called "router on a stick".

Configuring Router on a Stick

To configure a router on a stick, follow these steps:

1. Enter the configuration mode on the router by typing configure terminal.
2. Create subinterfaces on the router's physical interface for each VLAN using the interface fastethernet 0/0.1 command. Replace 0/0.1 with the desired subinterface number.
3. Configure encapsulation for the subinterface using the encapsulation dot1q [vlan_id] command. Replace [vlan_id] with the corresponding VLAN ID.
4. Assign an IP address to each subinterface using the ip address [ip_address] [subnet_mask] command. Replace [ip_address] and [subnet_mask] with the appropriate values.
5. Repeat steps 2 to 4 for each VLAN that requires inter-VLAN routing.
6. Exit configuration mode by typing exit.
7. Verify the subinterface configuration using the show ip interface brief command.

Testing Inter-VLAN Communication

To test inter-VLAN communication, follow these steps:

1. Configure IP addresses on the devices within each VLAN, making sure they are in the appropriate IP range for their respective subnets.
2. Attempt to ping devices in different VLANs to verify connectivity.
3. If the pings are successful, inter-VLAN communication is working correctly.

Pros and Cons of Using Inter-VLAN Routing

Pros of Inter-VLAN Routing

• ✅ Improved network performance and security through logical segmentation of traffic.
• ✅ Efficient use of network resources and simplified network administration.
• ✅ Flexibility in network configuration and easy scalability.
• ✅ Enhanced network troubleshooting and fault isolation.

Cons of Inter-VLAN Routing

• ❌ Increased administrative complexity compared to a simpler network design.
• ❌ Potential performance degradation due to increased routing overhead.
• ❌ Requires additional configuration and networking equipment.
• ❌ Inefficient use of bandwidth when unnecessary traffic is routed between VLANs.

Frequently Asked Questions (FAQs)

📌 How do VLANs improve network performance?

VLANs improve network performance by reducing collision domains and optimizing the use of available network resources. By segmenting network traffic, VLANs minimize unnecessary broadcast traffic and enable administrators to prioritize critical services, leading to improved overall network efficiency.

📌 Can I have multiple VLANs on a single switch?

Yes, it is possible to have multiple VLANs on a single switch. Each switch port can be assigned to a specific VLAN, allowing for logical network segmentation. This enables separate broadcast domains and facilitates better network management and security.

📌 What is the purpose of a trunk port?

A trunk port is used to carry traffic between switches or between a switch and a router. Trunk ports allow multiple VLANs to be transported over a single physical link by adding VLAN tags to each frame. This facilitates inter-VLAN communication and ensures that traffic is properly routed between VLANs.

📌 Are there any limitations of router on a stick?

While a router on a stick configuration provides a flexible and cost-effective solution for inter-VLAN routing, it has a few limitations. One limitation is the potential for reduced performance due to the router's processing capacity. Additionally, the use of a single physical link for all inter-VLAN traffic may result in bandwidth congestion if the link becomes saturated.

Resources

• Cisco VLAN Configuration Guide
• Understanding VLANs and How They Work