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Configuring InterVLAN Routing with Catalyst

3750/3560/3550 Series Switches
Document ID: 41260

Contents
Introduction
Prerequisites
Requirements
Components Used
Related Products
Conventions
Background Theory
Configure
Network Diagram
Configurations
Verify
Troubleshoot
Troubleshooting Procedure
Related Information

Introduction
This document explains how to configure interVLAN routing with Cisco Catalyst 3750/3560/3550 series
switches. The document provides a sample configuration for interVLAN routing with a Catalyst 3550 series
switch that runs enhanced multilayer image (EMI) software in a typical network scenario. The document uses
a Catalyst 2950 series switch and a Catalyst 2948G switch as Layer 2 (L2) closet switches that connect to the
Catalyst 3550. The Catalyst 3550 configuration also has a default route for all traffic that goes to the Internet
when the next hop points to a Cisco 7200VXR router. You can substitute a firewall or other routers for the
Cisco 7200VXR router.

Prerequisites
Requirements
Ensure that you meet these requirements before you attempt this configuration:
• Knowledge of how to create VLANs
For more information, refer to Creating Ethernet VLANs on Catalyst Switches.
• Knowledge of how to create VLAN trunks
For more information, refer to the Configuring VLAN Trunks section of Configuring VLANs.

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
• Catalyst 2950G−48 that runs Cisco IOS Software Release 12.1(12c)EA1 EI

The information in this document was created from the devices in a specific lab environment. installed on your switch. In the example in this document. You can forward these non−IP packets with fallback bridging. The switch receives a packet. make sure that you understand the potential impact of any command. so this document does not show the configuration. In order to use this feature. you must have the IP services image. The switch does not route non−IP packets between VLANs and routed ports. you are presented with the information to configure the features described in this document. Devices within a VLAN can communicate with each other without the need for routing.3(10) Note: The configuration from the Cisco 7200VXR is not relevant. All of the devices used in this document started with a cleared (default) configuration. formerly known as the enhanced multilayer image (EMI). Such a VLAN design also has an additional benefit. L2−only switches require an L3 routing device. The device is either external to the switch or in another module on the same chassis. The design allows the administrator to restrict communication between VLANs with use of access lists.• Catalyst 2948G that runs Catalyst OS (CatOS) version 6. If your network is live. you can use access lists to restrict the engineering VLAN from access to devices on the finance VLAN. An example is the 3550. Devices in separate VLANs require a routing device to communicate with one another. determines that the packet belongs to another VLAN. VLANs separate devices into different collision domains and Layer 3 (L3) subnets. and sends the packet to the appropriate port on the other VLAN. For example. and the finance VLAN only has devices that relate to finance. A typical network design segments the network based on the group or function to which the device belongs. Related Products This configuration can also be used with these hardware and software versions: • Any Catalyst 3750/3560/3550 switch that runs EMI software or standard multilayer image (SMI) Cisco IOS Software Release 12. A new breed of switches incorporate routing capability within the switch. Here is a link to a video (available on Cisco Support Community InterVLAN routing on a Catalyst 3550 series switch: ) that demonstrates how to configure the How To Configure InterVLAN Routing On Layer 3 Switches Configure In this section. the devices in each VLAN can talk to one another without the need for all the devices to be in the same broadcast domain.1(11)EA1 and later • Any Catalyst 2900XL/3500XL/2950/3550 or CatOS switch model. Background Theory In a switched network. the engineering VLAN only has devices that relate to the engineering department. If you enable routing. used as the access layer switch Conventions Refer to Cisco Technical Tips Conventions for more information on document conventions. .

which are the Catalyst 2950 and 2948G. are trunked to the Catalyst 3550 switch. . Therefore. By default. In order to make the switch function as an L3 device and provide interVLAN routing.3. the Catalyst 3550 switch acts as an L2 device with disablement of IP routing. For example.Note: Use the Command Lookup Tool commands used in this document. you must enable IP routing globally. (registered customers only) to find more information on the Network Diagram This document uses this network setup: In this diagram.1.1. traffic for which the 3550 does not have a routing table entry forwards to the 7200VXR for process. These VLANs are the three VLANs that the user defines: • VLAN 2user VLAN • VLAN 3server VLAN • VLAN 10management VLAN The default gateway configuration on each server and host device must be the VLAN interface IP address that corresponds on the 3550. for servers. The default route for the Catalyst 3550 points to the Cisco 7200VXR router. The access layer switches. The Catalyst 3550 uses this default route to route traffic destined for the Internet. the default gateway is 10. a small sample network with the Catalyst 3550 provides interVLAN routing between the various segments.

The management VLAN is different from the user or server VLAN. If the native VLAN on one end of the trunk is different than the native VLAN on the other end. you can easily replace a Cisco 7200VXR router with a firewall that connects to the Internet gateway router. This example configures a static default route on the 3550 instead. • Do not run a routing protocol between the Catalyst 3550 and the Internet gateway router. EtherChannel also provides link redundancy in the case of a link failure. • If you have two Catalyst 3550 switches in your network. refer to the Configuring HSRP section of Configuring IP Services. In this example. the traffic of the native VLANs on both sides cannot be transmitted correctly on the trunk.1 no service single−slot−reload−enable no service pad service timestamps debug uptime service timestamps log uptime no service password−encryption ! hostname Cat3550 ! ! ip subnet−zero !−−− Enable IP routing for interVLAN routing. • Separate the management VLAN from the user or server VLAN. any broadcast/packet storm that occurs in the user or server VLAN does not affect the management of switches. as the second tip explains. For more information on the configuration of HSRP.. ip routing !! ! . Configurations This document uses these configurations: • Catalyst 3550 • Catalyst 2950 • Catalyst 2948G Catalyst 3550 (Catalyst 3550−48 Switch) Cat3550#show running−config Building configuration. This step is very important because this configuration does not use routing protocols. • Use a Layer 3 (routed) port to connect to the default gateway port. Current configuration : 3092 bytes ! version 12. • Do not use VLAN 1 for management.1Q trunk is the same on both ends of the trunk link. you can dual connect the access layer switches to both 3550 switches. This setup is best if there is only one route to the Internet. Make sure to configure static routes. The use of VLAN 1 for management can cause potential issues for the management of switches. you can configure EtherChannel.. • If you need additional bandwidth for the uplink ports. preferably summarized.Practical Tips • Ensure that the native VLAN for an 802. as in this diagram. and any devices that connect to nonconfigured ports are in VLAN 1. All ports in Catalyst switches default to VLAN 1. Run Hot Standby Router Protocol (HSRP) between the switches to provide redundancy in the network. on the gateway router (7200VXR) for subnets that can be reached by the Catalyst 3550. This failure to transmit correctly can imply some connectivity issues in your network. With this separation.

with negotiation.255.1 255. If you establish a trunk link with the default trunking mode. Refer to !−−− Using PortFast and Other Commands to Fix Workstation Startup Connectivity Delays !−−− for more information.252 ! interface GigabitEthernet0/1 description To 2950 !−−− !−−− !−−− !−−− !−−− !−−− !−−− !−−− Configure IEEE 802. on the L2 switch. ! interface FastEthernet0/48 description To Internet_Router !−−− The port that connects to the router converts into a routed (L3) port.1 (dot1q) trunking.1. Use the show interfaces trunk command to verify the establishment of the trunk. switchport access vlan 3 !−−− Configure the port to be an access port to prevent trunk negotiation delays.1. VLAN 3. ip address 200. If there is not support for Dynamic Trunking Protocol (DTP) on the far switch. switchport trunk encapsulation dot1q no ip address ! interface GigabitEthernet0/2 description To 2948G switchport trunk encapsulation dot1q no ip address ! interface Vlan1 no ip address .spanning−tree extend system−id ! ! ! interface FastEthernet0/1 no ip address ! !−−− Output suppressed. the trunk does not appear in the configuration. switchport mode access no ip address !−−− Configure PortFast for initial Spanning Tree Protocol (STP) delay. issue the switchport mode trunk command to force the switch port to trunk mode. even though a trunk has been established on the interface. spanning−tree portfast ! !−−− Output suppressed.255. Note: The default trunking mode is dynamic auto. ! interface FastEthernet0/5 description to SERVER_1 !−−− Configure the server port to be in the server VLAN. no switchport !−−− Configure the IP address on this port.

2 ip http server ! ! ! line con 0 line vty 5 15 ! end Note: Since the 3550 has configuration as a VLAN Trunk Protocol (VTP) server.0. ip address 10.0 200.shutdown ! interface Vlan2 description USER_VLAN !−−− This IP address is the default gateway for users.. Current configuration : 2883 bytes ! version 12.3.0 ! interface Vlan3 description SERVER_VLAN !−−− This IP address is the default gateway for servers.255.0.0 ! ip classless !−−− This route statement allows the 3550 to send Internet traffic to !−−− the default router which.0.0 0. ip address 10.1.255.255. ip route 0.1 no service single−slot−reload−enable no service pad service timestamps debug uptime .0 ! interface Vlan10 description MANAGEMENT_VLAN !−−− This IP address is the default gateway for other L2 switches. ip address 10. This behavior is standard.1 255.1.1 255.1.1 255.255. in this case. is the 7200VXR (Fe 0/0 interface)..255. This switch uses these commands to create a VTP server with the three VLANs that the user defined from global configuration mode: Cat3550(config)#vtp domain cisco Cat3550(config)#vtp mode server Cat3550(config)#vlan 2 Cat3550(config−vlan)#name USER_VLAN Cat3550(config−vlan)#exit Cat3550(config)#vlan 3 Cat3550(config−vlan)#name SERVER_VLAN Cat3550(config−vlan)#exit Cat3550(config)#vlan 10 Cat3550(config−vlan)#name MANAGEMENT Catalyst 2950 (Catalyst 2950G−48 Switch) Cat2950#show running−config Building configuration. the switch does not display the VTP configuration.2.1.255.10.1.0.

VLAN 2.1.service timestamps log uptime no service password−encryption ! hostname Cat2950 ! ! ip subnet−zero ! spanning−tree extend system−id ! ! interface FastEthernet0/1 no ip address ! !−−− Output suppressed. switchport access vlan 2 switchport mode access no ip address spanning−tree portfast ! !−−− Output suppressed.2 255. interface FastEthernet0/16 no ip address ! interface FastEthernet0/17 description SERVER_2 switchport access vlan 3 switchport mode access no ip address spanning−tree portfast ! !−−− Output suppressed.10.255. interface GigabitEthernet0/1 switchport trunk encapsulation dot1q no ip address ! interface GigabitEthernet0/2 no ip address ! interface Vlan1 no ip address no ip route−cache shutdown ! interface Vlan10 description MANAGEMENT !−−− This IP address manages this switch. ip address 10. ! interface FastEthernet0/33 description HOST_1 !−−− Configure HOST_1 to be the user VLAN.255.0 no ip route−cache ! .

.... This behavior is standard... the VTP server. The 2950 acquires the VLAN information from the VTP server... The gateway points to the VLAN 10 interface on the 3550. .10. This 2950 switch uses these commands to make the switch a VTP client in the VTP domain cisco from global configuration mode: Cat2950(config)#vtp domain cisco Cat2950(config)#vtp mode client Catalyst 2948G Switch Cat2948G> (enable) show config This command shows non−default configurations only.. Use 'show config all' to show both default and non−default configurations... begin ! # ***** NON−DEFAULT CONFIGURATION ***** ! ! #time: Fri Jun 30 1995.1 ip http server ! ! line con 0 line vty 5 15 ! end Note: Since the Catalyst 2950 has configuration as a VTP client. which is the 3550.3(10) ! ! #system web interface version(s) ! #test ! #system set system name Cat2948G ! #frame distribution method set port channel all distribution mac both ! #vtp !−−− Configure the VTP domain to be the same as the 3550. ip default−gateway 10........... . 05:04:47 ! #version 6...1.... set vtp mode client ! #ip !−−− Configure the management IP address in VLAN 10. .. the switch does not display the VTP configuration. set vtp domain cisco !−−− Choose the VTP mode as client for this switch.!−−− Configure the default gateway so that the switch is reachable from other !−−− VLANs/subnets...

0 10.255.0. Catalyst 3550 • show vtp status Cat3550#show vtp status VTP Version : 2 Configuration Revision : 3 Maximum VLANs supported locally : 1005 Number of existing VLANs : 8 VTP Operating Mode : Server VTP Domain Name : cisco VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x54 0xC0 0x4A 0xCE 0x47 0x25 0x0B 0x49 Configuration last modified by 200. set ip route 0.0/0.0. Use the OIT to view an analysis of show command output.1q 802.1q Port Vlans allowed on trunk Status trunking trunking Native vlan 1 1 .bin ! #module 1 : 0−port Switching Supervisor ! #module 2 : 50−port 10/100/1000 Ethernet !−−− Configure HOST_2 and SERVER_3 ports in respective VLANs.1. The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands.10.1.10.1.255 set interface sl0 down set interface me1 down !−−− Define the default route so that the switch is reachable.1 ! #set boot command set boot config−register 0x2 set boot system flash bootflash:cat4000.1 on interface Vl2 (lowest numbered VLAN interface found) • show interfaces trunk Cat3550#show interfaces trunk Port Gi0/1 Gi0/2 Mode desirable desirable Encapsulation 802. set trunk 2/49 desirable dot1q 1−1005 end Verify This section provides information you can use to confirm your configuration works properly.set interface sc0 10 10.3/255.1.1.6−3−10.2.10.0.0.1 at 3−1−93 01:06:24 Local updater ID is 10. set set set set vlan vlan port port 2 2/2 3 2/23 name name 2/2 To HOST_2 2/23 to SERVER_3 !−−− Configure trunk to 3550 with dot1q encapsulation.0 10.1.255.

ia − IS−IS inter area * − candidate default. U − per−user static route.10 • show ip route Cat3550#show ip route Codes: C − connected.0.0.1.1.1.1. L1 − IS−IS level−1. R − RIP. O − OSPF.0.Gi0/1 Gi0/2 1−4094 1−4094 Port Gi0/1 Gi0/2 Vlans allowed and active in management domain 1−3.1. S − static. IA − OSPF inter area N1 − OSPF NSSA external type 1.10 1−3.3. Vlan10 10.2 C C C C S* Catalyst 2950 • show vtp status Cat2950#show vtp status VTP Version : 2 Configuration Revision : 3 Maximum VLANs supported locally : 250 Number of existing VLANs : 8 VTP Operating Mode : Client VTP Domain Name : cisco VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x54 0xC0 0x4A 0xCE 0x47 0x25 0x0B 0x49 Configuration last modified by 200.10 .0/30 is subnetted.1. E2 − OSPF external type 2.0. N2 − OSPF NSSA external type 2 E1 − OSPF external type 1.0 is directly connected. o − ODR P − periodic downloaded static route Gateway of last resort is 200.10 1−3.2. M − mobile. 1 subnets 200.0/0 [1/0] via 200.0 200. Vlan2 0.0/24 is subnetted.1. 3 subnets 10.1.0 is directly connected.10. Vlan3 10.0 is directly connected.1.1. FastEthernet0/48 10.0 is directly connected.1.2 to network 0. B − BGP D − EIGRP.10 Port Vlans in spanning tree forwarding state and not pruned Gi0/1 Gi0/2 1−3.1q Status trunking Native vlan 1 Port Gi0/1 Vlans allowed on trunk 1−4094 Port Gi0/1 Vlans allowed and active in management domain 1−3.0. L2 − IS−IS level−2.0.10 Port Gi0/1 Vlans in spanning tree forwarding state and not pruned 1−3.1. I − IGRP. EX − EIGRP external.1.1 at 3−1−93 01:06:24 • show interfaces trunk Cat2950#show interfaces trunk Port Gi0/1 Mode desirable Encapsulation 802. E − EGP i − IS−IS.

. make sure that you have configured trunking properly. issue the show trunk command for CatOS or the show interfaces trunk command for Cisco IOS Software. make sure that you can ping the respective default gateway. Note: See Step 1. In order to check the configuration. If you are not able to ping devices in different VLANs.1. check the VLAN assignment of the source and destination ports to make sure that the source and destination are in the same VLAN.10 Port −−−−−−−− 2/49 Vlans in spanning tree forwarding state and not pruned −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− 1−3.Catalyst 2948G • show vtp domain Cat2948G> (enable) show vtp domain Domain Name Domain Index VTP Version Local Mode Password −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−− −−−−−−−−−−− −−−−−−−−−−− −−−−−−−−−− cisco 1 2 client − Vlan−count Max−vlan−storage Config Revision Notifications −−−−−−−−−− −−−−−−−−−−−−−−−− −−−−−−−−−−−−−−− −−−−−−−−−−−−− 8 1023 3 disabled Last Updater V2 Mode Pruning PruneEligible on Vlans −−−−−−−−−−−−−−− −−−−−−−− −−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−− 200. Also.1.10 Troubleshoot Use this section to troubleshoot your configuration. check that the native VLAN matches on either side. If you are not able to ping devices within the same VLAN. Troubleshooting Procedure Follow these instructions: 1. In order to check the VLAN assignment. If the source and destination are not in the same switch. 2. issue the show port mod/port command for CatOS or the show interface status command for Cisco IOS Software. Make sure that the subnet mask matches between the source and destination devices.1 disabled disabled 2−1000 • show trunk Cat2948G> (enable) show trunk * − indicates vtp domain mismatch Port Mode Encapsulation −−−−−−−− −−−−−−−−−−− −−−−−−−−−−−−− 2/49 desirable dot1q Status −−−−−−−−−−−− trunking Native vlan −−−−−−−−−−− 1 Port −−−−−−−− 2/49 Vlans allowed on trunk −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− 1−1005 Port −−−−−−−− 2/49 Vlans allowed and active in management domain −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− 1−3.

make sure that the default route on the 3550 points to the correct IP address. Make sure that the Internet gateway router has routes to the Internet and the internal networks. All rights reserved. issue the show ip interface interface−id command and the show ip route command. 2012 Document ID: 41260 . Terms & Conditions | Privacy Statement | Cookie Policy | Trademarks of Cisco Systems. Related Information • Creating Ethernet VLANs on Catalyst Switches • LAN Product Support • LAN Switching Technology Support • Technical Support & Documentation − Cisco Systems Contacts & Feedback | Help | Site Map © 2013 − 2014 Cisco Systems. make sure that the default gateway of the device points to the correct VLAN interface IP address. In order to check. Inc. Updated: Feb 23. Inc. 3.Also. Make sure that the subnet mask matches. If you are not able to reach the Internet. and that the subnet address matches the Internet gateway router.