How To Configure InterVLAN Routing on Layer 3 Switches?

Introduction

VLANs divide broadcast domains in a LAN environment. Whenever hosts in one VLAN need to communicate with hosts in another VLAN, the traffic must be routed between them. This is known as inter-VLAN routing. On Catalyst switches it is accomplished by creating Layer 3 interfaces (Switch virtual interfaces (SVI) ). This document provides the configuration and troubleshooting steps applicable to this capability.

Note: This document uses a Catalyst 3550 as an example. However, the concepts can also be applied to other Layer 3 switches that run Cisco IOS® (for example, Catalyst 3560, 3750, Catalyst 4500/4000 Series with Sup II+ or later, or Catalyst 6500/6000 Series that run Cisco IOS System software).

Prerequisites

Requirements

Catalyst switch models 3560, 3750, Catalyst 4500/4000 Series with Sup II+ or later, or Catalyst 6500/6000 Series that run Cisco IOS system software support basic InterVLAN routing features in all their supported software versions. Before you attempt this configuration on a 3550 series switch, ensure that you meet these prerequisites:

· InterVLAN routing on the Catalyst 3550 has certain software requirements to support interVLAN routing on the switch. See this table to determine whether your switch can support interVLAN routing.

Image Type and Version	InterVLAN Routing Capability
Enhanced Multilayer Image (EMI) - All Versions	Yes
Standard Multilayer Image (SMI) - prior to Cisco IOS Software Release12.1(11)EA1	No
Standard Multilayer Image (SMI) - Cisco IOS Software Release 12.1(11)EA1 and later	Yes

Components Used

The information in this document is based on these software and hardware versions:

· Catalyst 3550-48 that runs Cisco IOS Software Release 12.1(12c)EA1 EMI

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Configure InterVLAN Routing

Task

In this section, you are presented with the information to configure the features described in this document.

This logical diagram explains a simple interVLAN routing scenario. The scenario can be expanded to include a multi-switch environment by first configuring and testing inter-switch connectivity across the network before configuring the routing capability. For such a scenario that uses a Catalyst 3550, refer to Configuring InterVLAN Routing with Catalyst 3550 Series Switches.