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Cisco − How To Configure InterVLAN Routing on Layer 3 Switc

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

Before You Begin Conventions For more information on document conventions. however. This document provides the configuration and troubleshooting steps applicable to this capability. 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. Catalyst 4000 Series with Sup II+ or higher. see the Cisco Technical Tips Conventions.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.1(11)EA1 and later InterVLAN Routing Capability Yes No Yes Cisco − How To Configure InterVLAN Routing on Layer 3 Switches .1(11)EA1 Standard Multilayer Image (SMI) − 12. Note: This document uses a Catalyst 3550 as an example. or Catalyst 6000 Series running Cisco IOS on the Supervisor and MSFC). 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. the concepts can also be applied to other Layer 3 switches running Cisco IOS® (for example. Prerequisites Before attempting this configuration.

For such a scenario using a Catalyst 3550. Configuring InterVLAN Routing Task In this section. you are presented with the information to configure the features described in this document. please refer to the document Configuring InterVLAN Routing with Catalyst 3550 Series Switches. • Catalyst 3550−48 running 12. 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. • 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 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. Components Used The information in this document is based on the software and hardware versions below.For more information on the differences between SMI and EMI. The following logical diagram explains a simple interVLAN routing scenario. ensure that you understand the potential impact of any command before using it. If you are working in a live network. access ports and trunking on the 3550.1(12c)EA1 EMI Software release The information presented in this document was created from devices in a specific lab environment. If you need information on configuring VLANs. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches . All of the devices used in this document started with a cleared (default) configuration. refer to the document Upgrading Software Images on Catalyst 3550 Series Switches Using the Command Line Interface. The document also provides the procedure to upgrade the IOS code to a version that supports interVLAN routing.

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

4.255. End with CNTL/Z. Also notice that the IP address is in the same subnet as the default router. 7.0.0. in this case.2 From the diagram in the Task section.1. When the switch receives a packet destined for another subnet/VLAN. Use the show vlan command to verify that the VLANs exist in the VLAN database.255. one per line.3.1.1 255.. 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. If the switch receives a packet for a network not in the routing table. 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.0. the VLAN interfaces must be configured with an IP address. Exiting. Switch#conf t Enter configuration commands. In this scenario we have a Layer 3 FastEthernet port. For the switch to be able to route between the VLANs.255. However. Switch(config)#interface FastEthernet 0/1 Switch(config−if)#no switchport Switch(config−if)#ip address 200.1..255.1..0 Switch(config−if)#no shutdown Repeat this process for all VLANs identified in Step 1.1.2. Configure the default route for the switch Switch(config)#ip route 0.0 Switch(config−if)#no shutdown The no switchport command makes the interface Layer 3 capable. Configure the VLAN interfaces with the IP address identified in Step 4. 5. note that the IP address of the default router is 200.1.1.0 200. Note: The ip default−gateway command is used to specify the default gateway when routing is not enabled. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches . routing is enabled (from Step 1) hence the ip default−gateway command is unnecessary. you must add them on the switch. In its place. Determine the IP addresses you want to assign to the VLAN interface on the switch. the switch looks at the routing table to determine where to forward the packet.1 255. 6. configure an IP address for that VLAN interface. Note: This step can be omitted if the switch can reach the default router through a VLAN. Configure the interface to the default router. Refer to the document Understanding and Configuring VLAN Trunk Protocol (VTP). If they do not exist.0.0 0. Tip: You can use VTP to propagate these VLANs to other switches.2. Switch(config)#interface Vlan2 Switch(config−if)#ip address 10. it forwards it to the default gateway for further processing From the switch verify that you can ping the default router.

0.1. • show ip interface brief − Lists a brief summary of an interface's IP information and status. R − RIP.0 is directly connected. FastEthernet0/48 10. Troubleshooting Procedure Below is troubleshooting information relevant to this configuration. Vlan3 10. Configure your end devices to use the respective Catalyst 3550 VLAN interface as their default gateway For example. ♦ If you are not able to ping between two devices on the same VLAN on the same switch.0.10.0 is directly connected. Troubleshoot This section provides information you can use to troubleshoot your configuration. L1 − IS−IS level−1. M − mobile.2. Follow the instructions to troubleshoot your configuration. Hence.3. U − per−user static route.0. Vlan2 0.1. Certain show commands are supported by the Output Interpreter Tool ( registered customers only) . devices in VLAN 2 should use the interface VLAN 2 IP address as its default gateway. the default route with the next hop 200. B − BGP D − EIGRP. ia − IS−IS inter area * − candidate default. Refer to the appropriate client configuration guide for more information on designating the default gateway. verify that your source and destination ports have devices connected to them and are assigned to the same VLAN. Cat3550#show ip route Codes: C − connected. 3 subnets 10.1.1.0. This command can be used to verify that the VLAN interfaces and ports on the switch are up/up. I − IGRP. N2 − OSPF NSSA external type 2 E1 − OSPF external type 1. Also. which allows you to view an analysis of show command output.1.2 to network 0. S − static.2 allows the switch to forward traffic to the gateway of last resort (for traffic the switch cannot route).0 is directly connected.1.0/0 [1/0] via 200.0.1. refer to the document Creating Ethernet VLANs Cisco − How To Configure InterVLAN Routing on Layer 3 Switches .1.8. 1 subnets 200. Vlan10 10. O − OSPF. Verify This section provides information you can use to confirm your configuration is working properly.2 Note that the routing table has an entry for each VLAN interface subnet. 1. VLAN 2 and vice versa. Verify you have Layer 2 connectivity by issuing ICMP pings.1.1. For more information. o − ODR P − periodic downloaded static route Gateway of last resort is 200. devices in VLAN 3 can communicate with devices in VLAN 10. L2 − IS−IS level−2.1.0/30 is subnetted. E − EGP i − IS−IS. E2 − OSPF external type 2.0.1. IA − OSPF inter area N1 − OSPF NSSA external type 1. • show ip route − Provides a snapshot of the routing table entries. EX − EIGRP external.1.0 C C C C S* 200.0 is directly connected.0/24 is subnetted.

1. Also verify that the IP address and subnet mask on the switch are configured correctly. In this example we would ping from VLAN 2 (10.2) and ping Interface VLAN 2 (10. 5. issue the no shutdown command in the VLAN interface configuration mode. 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). ♦ If the interface status is administratively down.1) or Interface VLAN 10 (10. All rights reserved. Inc.on Catalyst Switches. a device on VLAN 2 should be able to ping a device on VLAN 3.1. In this example.1) to Interface VLAN 3 (10. Cisco − How To Configure InterVLAN Routing on Layer 3 Switches .10. verify that the host's default gateway points to the corresponding VLAN interface IP address and that the subnet masks match. verify that the default route on the 3550 is pointing to the correct IP address on the default router.2. If you are not able to ping the interface. For example. ♦ If you are not able to ping between two devices on the same VLAN but not on the same switch. the default gateway of the device on VLAN 2 should point to Interface VLAN 2 (10. verify the VTP configuration and that the VLANs have been added to the VLAN database.1. 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. If the ping test was successful in step 3. ♦ If the interface status is down/down. 2.1). Initiate a ICMP ping from an end device connected to the Catalyst 3550 to its corresponding VLAN interface. you could use a host on VLAN 2 (10. 4.1.2.2. verify that trunking is configured properly and that the native VLAN matches on both sides of the trunk. but fails to reach the end device on other VLAN.1. If you are not able to reach the Internet or corporate network. For example. 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. 3. You should also check to see if a port is assigned to the VLAN and whether it is in the Spanning Tree forwarding state.3.1). Initiate a ping from the end device in one VLAN to the end device in another VLAN. verify that the default gateway on the connected device is configured correctly. Important Notices and Privacy Statement.1.2. If the ping fails.