Cisco − How To Configure InterVLAN Routing on Layer 3 Switc

.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................1 Introduction................................................................................................................................2 Configuring InterVLAN Routing..........................................6 i .......................................5 Troubleshooting Procedure.....................1 Components Used..1 Before You Begin..........................................................................3 Verify.........................................................................................................................2 Task................................................Cisco − How To Configure InterVLAN Routing on Layer 3 Switches Table of Contents How To Configure InterVLAN Routing on Layer 3 Switches.......................................5 Troubleshoot........................................................................................................................................................................1 Conventions.................................1 Prerequisites..................................................................................................2 Step−by−Step Instructions................................................................................................................................................................................................................................................................................................................5 Related Information.

please ensure that you meet the following prerequisites: • InterVLAN routing on the Catalyst 3550 has certain software requirements to support interVLAN routing on the switch. see the Cisco Technical Tips Conventions. Please refer to the table below to determine whether your switch can support interVLAN routing Image Type and Version Enhanced Multilayer Image (EMI) − All Versions Standard Multilayer Image (SMI) − prior to 12. or Catalyst 6000 Series running Cisco IOS on the Supervisor and MSFC).How To Configure InterVLAN Routing on Layer 3 Switches Introduction Before You Begin Conventions Prerequisites Components Used Configuring InterVLAN Routing Task Step−by−Step Instructions Verify Troubleshoot Troubleshooting Procedure Related Information Introduction Layer 3 Catalyst switches incorporate routing functionality which allows the switch to perform interVLAN routing. Catalyst 4000 Series with Sup II+ or higher. Note: This document uses a Catalyst 3550 as an example. Before You Begin Conventions For more information on document conventions.1(11)EA1 Standard Multilayer Image (SMI) − 12.1(11)EA1 and later InterVLAN Routing Capability Yes No Yes Cisco − How To Configure InterVLAN Routing on Layer 3 Switches . Prerequisites Before attempting this configuration. the concepts can also be applied to other Layer 3 switches running Cisco IOS® (for example. This document provides the configuration and troubleshooting steps applicable to this capability. however.

For more information on the differences between SMI and EMI. For such a scenario using a Catalyst 3550. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network. access ports and trunking on the 3550. please refer to the document Configuring InterVLAN Routing with Catalyst 3550 Series Switches. you are presented with the information to configure the features described in this document.1(12c)EA1 EMI Software release The information presented in this document was created from devices in a specific lab environment. ensure that you understand the potential impact of any command before using it. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches . please refer to Creating Ethernet VLANs on Catalyst Switches or the Catalyst 3550 Software Configuration Guide for the specific IOS version you are running on the switch. 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. The following logical diagram explains a simple interVLAN routing scenario. Configuring InterVLAN Routing Task In this section. Components Used The information in this document is based on the software and hardware versions below. • Catalyst 3550−48 running 12. If you need information on configuring VLANs. • This document assumes that layer 2 has been configured and that the devices within the same VLAN connected to the 3550 can communicate with one another. The document also provides the procedure to upgrade the IOS code to a version that supports interVLAN routing. refer to the document Upgrading Software Images on Catalyst 3550 Series Switches Using the Command Line Interface.

Step−by−Step Instructions Do the following to configure a switch to perform interVLAN routing. The command. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches . Even if IP routing was previously enabled. Make note of the VLANs that you want to route between. In our example. will appear towards the top of the output. or an EMI image. 1. Switch(config)#ip routing Note: If the switch does not accept the ip routing command. you will need to upgrade to either SMI image 12. Refer to the Prerequisites section for more information. this step ensures that it is indeed activated. Enable routing on the switch using the ip routing command. and repeat this step. we want to route traffic between VLANs 2. Tip: Check the show running−configuration and verify whether ip routing is enabled. hostname Switch ! ! ip subnet−zero ip routing ! vtp domain Cisco vtp mode transparent 2. 3 and 10. if enabled.1(11)EA1 or later.

1. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches .2. 5.0 200. 4. Determine the IP addresses you want to assign to the VLAN interface on the switch. Switch#conf t Enter configuration commands.255. the VLAN interfaces must be configured with an IP address.1. When the switch receives a packet destined for another subnet/VLAN. End with CNTL/Z. Configure the default route for the switch Switch(config)#ip route 0. 6.1.1 255. one per line.2. Switch#vlan database Switch(vlan)#vlan 2 VLAN 2 added: Name: VLAN0002 Switch(vlan)#vlan 3 VLAN 3 added: Name: VLAN0003 Switch(vlan)#vlan 10 VLAN 10 added: Name: VLAN0010 Switch(vlan)#exit APPLY completed.255. For the switch to be able to route between the VLANs. Refer to the document Understanding and Configuring VLAN Trunk Protocol (VTP). Tip: You can use VTP to propagate these VLANs to other switches.0. Switch(config)#interface FastEthernet 0/1 Switch(config−if)#no switchport Switch(config−if)#ip address 200. you must add them on the switch.1 255. The packet is then passed to the VLAN interface of the destination and in turn it is sent to the port where the end device is attached.2 From the diagram in the Task section.1. However. In its place.0 Switch(config−if)#no shutdown Repeat this process for all VLANs identified in Step 1. Configure the interface to the default router. Switch(config)#interface Vlan2 Switch(config−if)#ip address 10.0. Exiting. configure an IP address for that VLAN interface.1. Also notice that the IP address is in the same subnet as the default router. the switch looks at the routing table to determine where to forward the packet. in this case.255. note that the IP address of the default router is 200.255.. Note: This step can be omitted if the switch can reach the default router through a VLAN.0. Configure the VLAN interfaces with the IP address identified in Step 4.1.1.0 0.3. Use the show vlan command to verify that the VLANs exist in the VLAN database. 7. it forwards it to the default gateway for further processing From the switch verify that you can ping the default router. In this scenario we have a Layer 3 FastEthernet port. Note: The ip default−gateway command is used to specify the default gateway when routing is not enabled..0 Switch(config−if)#no shutdown The no switchport command makes the interface Layer 3 capable. If the switch receives a packet for a network not in the routing table. routing is enabled (from Step 1) hence the ip default−gateway command is unnecessary.. If they do not exist.0.

0. Verify This section provides information you can use to confirm your configuration is working properly. Vlan3 10. Hence.0/24 is subnetted.1.0 C C C C S* 200. • show ip interface brief − Lists a brief summary of an interface's IP information and status. IA − OSPF inter area N1 − OSPF NSSA external type 1. M − mobile.1.0/30 is subnetted. Cat3550#show ip route Codes: C − connected. 1.0 is directly connected. EX − EIGRP external. VLAN 2 and vice versa. Follow the instructions to troubleshoot your configuration. Configure your end devices to use the respective Catalyst 3550 VLAN interface as their default gateway For example.0 is directly connected.1. FastEthernet0/48 10. This command can be used to verify that the VLAN interfaces and ports on the switch are up/up. R − RIP.0.1.0 is directly connected. E − EGP i − IS−IS.1. N2 − OSPF NSSA external type 2 E1 − OSPF external type 1. ♦ If you are not able to ping between two devices on the same VLAN on the same switch.0/0 [1/0] via 200.2 Note that the routing table has an entry for each VLAN interface subnet. which allows you to view an analysis of show command output. ia − IS−IS inter area * − candidate default. B − BGP D − EIGRP.0 is directly connected.0. devices in VLAN 3 can communicate with devices in VLAN 10. Also. U − per−user static route. o − ODR P − periodic downloaded static route Gateway of last resort is 200. S − static. For more information.1.1. Vlan2 0.1. Verify you have Layer 2 connectivity by issuing ICMP pings. O − OSPF. L1 − IS−IS level−1. 3 subnets 10. devices in VLAN 2 should use the interface VLAN 2 IP address as its default gateway.0. I − IGRP.1.1. the default route with the next hop 200.2. verify that your source and destination ports have devices connected to them and are assigned to the same VLAN.2 allows the switch to forward traffic to the gateway of last resort (for traffic the switch cannot route).0.1.10. L2 − IS−IS level−2. Certain show commands are supported by the Output Interpreter Tool ( registered customers only) . 1 subnets 200.0.1.8.1. E2 − OSPF external type 2. Troubleshoot This section provides information you can use to troubleshoot your configuration. Refer to the appropriate client configuration guide for more information on designating the default gateway.3. refer to the document Creating Ethernet VLANs Cisco − How To Configure InterVLAN Routing on Layer 3 Switches .2 to network 0. • show ip route − Provides a snapshot of the routing table entries. Vlan10 10. Troubleshooting Procedure Below is troubleshooting information relevant to this configuration.

All rights reserved.1). verify that IP routing is enabled and that the VLAN interfaces status is up by issuing the show ip interface brief command.Also verify the interface VLAN status by issuing the show ip interface brief command.1). Initiate a ICMP ping from an end device connected to the Catalyst 3550 to its corresponding VLAN interface. a device on VLAN 2 should be able to ping a device on VLAN 3. If you are not able to ping the interface. If the ping test was successful in step 3.on Catalyst Switches.1). For example. the default gateway of the device on VLAN 2 should point to Interface VLAN 2 (10. For example. Initiate a ping from the end device in one VLAN to the end device in another VLAN. ♦ If you are not able to ping between two devices on the same VLAN but not on the same switch.1) to Interface VLAN 3 (10. ♦ If the interface status is down/down. In this example we would ping from VLAN 2 (10. 3.1.1) or Interface VLAN 10 (10. issue the no shutdown command in the VLAN interface configuration mode.3. ♦ If the interface status is administratively down. In this example. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches . you could use a host on VLAN 2 (10.2. but fails to reach the end device on other VLAN.1.2) and ping Interface VLAN 2 (10.1. Also verify that the IP address and subnet mask on the switch are configured correctly. If you are not able to reach the Internet or corporate network. 5. Initiate a ping from an end device in one VLAN to the interface VLAN on another VLAN to verify that the switch can route between VLANs. verify that the host's default gateway points to the corresponding VLAN interface IP address and that the subnet masks match. Related Information • Configuring InterVLAN Routing with Catalyst 3550 Series Switches • Configuring Layer 3 Interfaces for the Catalyst 4000 • Technical Support − Cisco Systems All contents are Copyright © 1992−2003 Cisco Systems. 4. 2.2. verify the VTP configuration and that the VLANs have been added to the VLAN database.2.2. Inc.1. verify that the default route on the 3550 is pointing to the correct IP address on the default router. Important Notices and Privacy Statement.1.1. You should also check to see if a port is assigned to the VLAN and whether it is in the Spanning Tree forwarding state. If the ping fails. verify that trunking is configured properly and that the native VLAN matches on both sides of the trunk.10. verify that the default gateway on the connected device is configured correctly.