SVI InterVLAN Routing

SVI InterVLAN Routing is a method that allows Layer 3 switches to route traffic between VLANs without relying on an external router.

Before going deeper, you might wonder: What exactly is a Layer 3 switch?

Figure 1 – Layer 3 switch concept

Layer 3 Switch Concept

A Layer 3 switch looks like a standard switch, but it can also perform routing.
It handles:

• Layer 2 switching for forwarding frames.

• Layer 3 routing, directly in hardware using ASICs.

Because routing happens in hardware instead of software (like on a router), the performance is significantly higher.
This is why modern networks rely on Layer 3 switches to route traffic between VLANs efficiently.

To achieve this routing capability, the switch uses SVIs.

What is an SVI?

An SVI (Switched Virtual Interface) is a virtual Layer 3 interface created for a specific VLAN on a Layer 3 switch.
Each VLAN has its own SVI, and that SVI becomes the default gateway for every device inside that VLAN.

Let’s look at the topology together:

Figure 2 – SVI routing topology

In this setup:

• A Layer 3 switch connects devices in VLAN 10 and VLAN 20

• Each VLAN has its own SVI, acting as the default gateway:

  • SVI for VLAN 10 → 192.168.1.1

  • SVI for VLAN 20 → 192.168.2.1

These SVI interfaces serve as the Layer 3 gateways, allowing the switch to route traffic internally between VLAN 10 and VLAN 20 without using any external router.

This is the modern and recommended method for inter-VLAN communication in enterprise networks.

Now that you understand what an SVI is, let’s walk through the configuration together.

Figure 3 – SVI routing topology

Step 1 — Create VLANs on the Layer 3 Switch

We start by creating the VLANs on the Layer 3 switch: