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Configure Inter VLAN Routing on Cisco Catalyst Switches

     Introduction
     Requirements
     Inter VLAN Routing Overview
     Connect to the Switch
     Configure Inter VLAN Routing on the Switch
     Verify your configuration
     Next Step
     Troubleshoot the Procedure
     Related Information

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Introduction

This document provides instructions on how to configure Inter VLAN routing on your Cisco Catalyst Switches. This procedure applies to Cisco Catalyst 3550, 3560, 3750 and 4500 series switches which runs Cisco IOS software.

Requirements

To perform the steps described in this document, you need these items:

Complete the initial configuration of the switch as instructed in, Configure a Catalyst Switch with Cisco Network Assistant.
A console cable. Refer to, Cable Descriptions for more information about cables.
Terminal emulation software such as HyperTerminal.
A switch that runs Cisco IOS Software Release 12.1(11)EA1 or later for SMI images or any EMI image.
Complete the Switch Port Assignment Worksheets as instructed in the Site Survey.

Inter VLAN Routing Overview

VLANs are used to separate a switched network into different broadcast domains, where each VLAN is a separate broadcast domain. Devices in each VLAN can communicate with other devices of the same VLAN. For communicating with devices of other VLANs routing is required to be done between the VLANs, and this is known as inter VLAN routing. For switches that do not support the routing feature (e.g. Catalyst 2950) a separate router, connected to the switch, is required to do routing between the VLANs. Catalyst 3550, 3560, 3750 and 4500 series switches support inter VLAN routing.

This document assumes that all the devices are directly connected to the switch on which inter VLAN routing needs to be configured. This switch, then connects to a router that is used to route the traffic destined to the outside network or to the Internet. This connection is done via interface FastEthernet 0/1 on the switch. However, if you have devices that connect to a separate switch that connects to the switch on which inter VLAN routing is to be configured, make sure the link between these two switches is a trunk. The default gateway for devices connected to the switch is the VLAN interface ip address of the respective VLAN to which the device belongs.

Note: To restrict certain VLANs from participating in inter VLAN routing, you need to use ACLs to deny communication between them. Refer to, ACL configuration on Catalyst switches using CLI.

Connect to the Switch

Follow these steps to connect your PC to the switch for configuration:

Connect a PC to the switch with a console cable.
Create a HyperTerminal connection to your switch. Refer to, Create a HyperTerminal Connection for more information.
Log into the switch with the login and password that you entered in fields B10 and B11 of the Switch Worksheet.
```
Username:admin
Password:
```
Type enable and press Enter to access the privileged mode. Type the enable password that you entered in field S5 of the Switch Port Assignment Worksheet.
```
switch>enable
Password:
```

Configure Inter VLAN Routing on the Switch

Follow these steps to configure switch for inter VLAN routing:

Enter the global configuration mode.
1. Create the VLANs, if they are not already created. Use the vlan command followed by vlan id.
2. Enter the exit command to come back to global configuration mode.
3. To configure the vlan, enter the interface vlan command followed by the vlan id of the vlan just created.
4. Assign an ip address to this VLAN, which acts as default gateway address to the devices in this VLAN, using the ip address command followed by an ip address and subnet mask.
5. Enter the no shutdown command to bring up the interface.
```
Switch#configure terminal
Switch(config)#vlan 21
Switch(config-vlan)#exit
Switch(config)#interface vlan 21
Switch(config-if)#ip address 192.168.11.1 255.255.255.0
Switch(config-if)#no shutdown
```
Note: Repeat this step to configure other VLANs on your switch, if not already configured.
To assign the interfaces to the respective VLAN, if not already assigned, use the interface command followed by the interface name and module number/port number in interface configuration mode.
1. Enter the switchport command to make this interface a Layer 2 interface.
2. Enter the switchport access vlan command followed by the respective vlan ID to which the port belongs.
3. Enter the no shutdown command to bring up the interface.
4. Enter the exit command to come out of the configuration mode.
```
Switch(config)#interface FastEthernet 0/2
Switch(config-if)#switchport
Switch(config-if)#switchport access vlan 21
Switch(config-if)#no shutdown
Switch(config-if)#exit
```
Note: Repeat this step to assign other switch interfaces to their respective VLANs, if not already assigned.
Enter the ip routing command to enable the routing feature globally on the switch.
```
Switch(config)#ip routing
```
Note: If the switch does not take this command, Cisco IOS does not support this feature. Upgrade Cisco IOS Software Release 12.1(11)EA1 or later for SMI images or to an EMI image and repeat this step.
Get into the interface that connects to the upstream router using the interface command followed by interface name, and then enter the no switchport command to make this interface Layer 3 capable.
```
Switch(config)#interface FastEthernet 0/1
Switch(config-if)#no switchport
```
Assign an appropriate ip address to this interface using the ip address command followed by an ip address and subnet mask, and enter the no shutdown command to bring up the interface.
```
Switch(config-if)#ip address 192.168.10.11 255.255.255.0
Switch(config-if)#no shutdown
```
Configure a default route on the switch to the upstream router for the traffic to the outside network or the Internet using the ip route command and the ip address of the upstream router at the end.
```
Switch(config)#ip route 0.0.0.0 0.0.0.0 192.168.10.1
```
Enter the end command to come out of the configuration mode. Enter the copy running-config startup-config command to save the configuration to NVRAM.
```
Switch(config)#end
Switch#copy running-config startup-config
```

Verify your configuration

Enter the show ip route command in the privilege exec mode and analyze the output. The output must contain one static default route to the upstream router and one entry for each VLAN configured on the switch.

Switch#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is 192.168.10.1 to network 0.0.0.0

C       192.168.10.0 is directly connected, FastEthernet 0/1
C       192.168.11.0 is directly connected, Vlan21
C       192.168.12.0 is directly connected, Vlan22
S*   0.0.0.0/0 [1/0] via 192.168.10.1

Next Step

You have completed Configuring Inter VLAN routing on your Cisco Catalyst Switch.

Refer to the Switch Support Page to make further changes to your switch.

Refer to the Configuration Overview Page to configure other devices in your network.

Troubleshoot the Procedure

This section provides information about common problems that you may encounter. If this information does not solve your problem, contact the SMB Technical Assistance Center (SMB TAC) for assistance.

Problem

Cause(s) and Suggested Solution(s)

The switch boots and displays several error messages but does not display a prompt in HyperTerminal.

Press Enter to clear the output and display the switch prompt.

Contact the SMB Technical Assistance Center (SMB TAC) for further assistance.