Mastering Inter VLAN Routing with Layer 3 Switch: A comprehensive guide


Welcome to our comprehensive guide on mastering Inter VLAN Routing using Layer 3 switches! In today's advanced networking landscape, it's essential for professionals to have a firm grasp of Inter VLAN Routing techniques and configurations. This article will walk you through the step by step process, covering everything from understanding the benefits of Inter VLAN Routing to troubleshooting common issues and implementing best practices.

Understanding Inter VLAN Routing with Layer 3 Switch

In this section, we'll discuss the benefits and differences between Layer 2 and Layer 3 switches, as well as the various methods of inter VLAN routing available with a Layer 3 switch.

Benefits of Inter VLAN Routing

Inter VLAN routing offers numerous benefits for organizations seeking to optimize their network infrastructure. One primary advantage is the improved scalability of the network topology. Due to its ability to route traffic across multiple VLANs, inter VLAN routing allows businesses to easily expand and manage an ever-growing number of devices in their IT environment without requiring additional hardware resources or complex configurations.

Another significant benefit of Inter VLAN routing is enhanced network security. By segregating hosts within different VLANs, administrators can effectively isolate sensitive data or specific applications from unauthorized access. This added layer of protection ensures that only designated users have access to specific resources on the network while preventing potential breaches that could compromise critical company assets. Furthermore, Inter VLAN routing fosters better overall performance by minimizing broadcast domains and reducing congestion in busy networks. For example, a large organization with various departments may choose to assign a separate VLAN for each unit – such as marketing, finance, and IT support teams – thus ensuring smooth communication within individual groups while also facilitating cross-functional collaboration when necessary.

Differences between Layer 2 and Layer 3 Switches


Layer 2 Switches

Layer 3 Switches

OSI Model Layer

Data Link Layer

Network Layer

Forwarding Mechanism

Based on MAC addresses

Based on IP addresses

Inter-VLAN Communication

Requires a router for communication

Can communicate directly with inter-VLAN routing


Less practical for large networks

Simplifies complex network designs


Higher costs for multiple routers

Reduced costs for small-to-medium-sized networks

Types of Inter VLAN Routing Methods

There are two main types of inter-VLAN routing methods used with Layer 3 switches

  • Router on a Stick (RoAS) − This method involves using a single interface on the router to connect to a Layer 2 switch. The switch, in turn, connects to multiple VLANs. The interface is configured as a trunk port, with each VLAN assigned a subinterface on the router. Traffic between the VLANs is routed through the subinterfaces on the router.

  • Switch Virtual Interfaces (SVIs) − This method involves assigning an IP address to each VLAN created on the Layer 3 switch. Each SVI functions as a virtual router for its respective VLAN and enables inter-VLAN communication. SVIs are typically used when there is no external router available to perform inter-VLAN routing.

Overall, both methods allow for efficient inter-VLAN routing and can be used depending on the network topology and requirements.

Configuring Inter VLAN Routing on Layer 3 Switches

To configure inter VLAN routing on Layer 3 switches, the basic configuration steps include enabling routing, configuring routed ports or subinterfaces for trunk links, setting up IP addresses for VLAN interfaces (VLANIF), and ensuring that all VLANs are properly configured.

Basic Configuration steps

To configure inter VLAN routing on a Layer 3 switch, the following basic configuration steps should be taken −

  • Choose the method for VLAN separation.

  • Assign an IP address and Subnet Mask to each VLAN interface.

  • Verify that IP Routing is enabled on the switch.

  • Create the respective VLANs and assign ports to their respective VLANs.

  • Map each VLAN to its appropriate interface or subinterface.

  • Configure the default gateway on each device.

These steps ensure that your Layer 3 switch is configured correctly and ready for InterVLAN communication, allowing multiple devices in different VLANs to communicate seamlessly with each other using Layer 3 Switch InterVLAN Routing techniques.

Configuring Routed ports

Configuring routed ports is an essential step in setting up inter VLAN routing using Layer 3 switches. These are the steps involved −

  • Identify the ports for inter VLAN communication and configure them as Layer 3 routed ports.

  • Assign a unique IP address and subnet mask to each routed port.

  • Remove any existing VLAN assignment with the "no switchport" command.

  • Configure an appropriate routing protocol for communication between VLANs

Properly configuring routed ports enables Layer 3 switches to function as inter VLAN routers, offering scalability and network segmentation capabilities crucial for modern networking infrastructures. Using commands like "ip address," "no switchport," and "ip routing" allows network administrators to establish and maintain efficient communication channels between different VLANs to achieve optimal performance levels.

Configuring VLAN Interfaces

Configuring VLAN interfaces is an essential step in implementing inter-VLAN routing on Layer 3 switches. Here are the basic steps to configure VLAN interfaces −

  • Access the switch command-line interface and enter global configuration mode.

  • Create a VLAN interface and assign an IP address and subnet mask.

  • Enable the VLAN interface with the "no shutdown" command.

By following these steps, you can successfully configure your Layer 3 switch for inter-VLAN routing and improve network efficiency and scalability.

Configuring SVIs

Configuring SVIs or Switched Virtual Interfaces is another way to implement inter-VLAN routing on a Layer 3 switch. Here are the steps to configure SVIs −

  • Enter global configuration mode.

  • Create an interface VLAN and assign an IP address to the interface.

  • Enable the interface and associate the VLAN with the SVI.

Virtual Router Redundancy Protocol (VRRP)

Virtual Router Redundancy Protocol (VRRP) is a redundancy protocol used for Layer 3 switching in inter-VLAN routing. VRRP allows multiple physical routers to act as a single virtual router with a shared IP address, improving fault tolerance and enabling faster failover times in case of hardware failures. It provides high availability and prevents disruptions caused by hardware outages or maintenance tasks.

Hot Standby Router Protocol (HSRP)

HSRP, on the other hand, allows multiple Layer 3 switches to act as an active and standby gateway IP address, providing fault tolerance and seamless network connectivity. If an HSRP-enabled switch fails, the standby switch takes over without interrupting network services. This ensures high availability of critical resources like servers or internet access points that rely on redundant gateways for constant availability.

Proper Network Segmentation

Breaking down a larger network into smaller subnetworks for better control over traffic flow and minimizing the risk of data breaches.

Understanding Routing Protocols

Routing protocols are crucial for inter-VLAN routing with Layer 3 switches, as they determine how network packets are forwarded between devices across multiple networks. They help find the best path for packet delivery, ensuring efficient and effective data transmission. Static routing involves manual route configuration by network administrators, while dynamic routing protocols, such as OSPF and EIGRP, automate the process by allowing routers to share real-time connection information.

Configuring QoS for Inter VLAN Traffic

  • Identify and categorize different types of traffic based on their importance/priority.

  • Assign and configure appropriate Quality of Service (QoS) policies to different types of traffic.

  • Specify bandwidth allocation for each category or type of network traffic.

  • Configure switches to use a specific queuing method for efficient prioritization and flow control.

  • Test and verify the QoS configuration to ensure optimal network performance.


In conclusion, mastering inter VLAN routing with Layer 3 switch is crucial for modern networking. With the ability to segment networks and improve scalability, inter-VLAN routing can greatly benefit companies of all sizes.

In this comprehensive guide, we have covered the basics of inter VLAN routing and the configuration process on Layer 3 switches. We have also discussed advanced techniques such as VRRP and HSRP, proper network segmentation principles, and troubleshooting tips.

By following best practices and regularly monitoring your network, you can ensure efficient and secure interconnectivity between VLANs. With this knowledge at your fingertips, you will be well-equipped to handle any challenges that come your way in maintaining a strong network infrastructure.

Updated on: 13-Apr-2023


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