Configuring Internal Routing on an IOS-Based Switch 594

Configuring Internal Routing on an IOS-Based Switch
At this stage of learning, it is a simple matter to configure internal routing. The configuration
on the modular L3SM is just about identical to that on the modern IOS-based layer 3 switches.
This example shows a 3550 configured as a VTP server, and with two VLANs configured. In
addition, two interfaces are placed into the created VLANs. No routing protocols are needed
unless the requirement exists to route outside the connected VLAN table.
Terry_3550# configure terminal
Terry_3550(config)#vtp domain globalnet
Terry_3550(config)#vtp mode server
Terry_3550(config)#vlan 2
Terry_3550(config-vlan)#name PRODUCTION
Terry_3550(config-vlan)#ip address 172.16.2.1 255.255.255.0
Terry_3550(config-vlan)#exit
Terry_3550(config)#vlan 3
Terry_3550(config-vlan)#name SALES
Terry_3550(config-vlan)#ip address 172.16.3.1 255.255.255.0
Terry_3550(config-vlan)#exit
Terry_3550(config)#vlan 1
Terry_3550(config-vlan)#ip address 172.16.1.1 255.255.255.0
Terry_3550(config-vlan)#exit
Terry_3550(config)#interface FastEthernet0/1
Terry_3550(config-if)#description PRODUCTION MANAGER
Terry_3550(config-if)#switchport access vlan 2
Terry_3550(config-if)#switchport mode access
Terry_3550(config)#interface FastEthernet0/2
Terry_3550(config-if)#description SALES MANAGER
Terry_3550(config-if)#switchport access vlan 3
Terry_3550(config-if)#switchport mode access
This gives rise to the following running configuration, viewed with the IOS standard show
running-config statement:
Terry_3550#show run
!
[output cut]
!
interface FastEthernet0/1
description PRODUCTION MANAGER
switchport access vlan 2

switchport mode access
no ip address
!
interface FastEthernet0/2
description SALES MANAGER
switchport access vlan 3
switchport mode access
no ip address
!
[output cut]
!
interface Vlan1
ip address 172.16.1.1 255.255.255.0
!
interface Vlan2
ip address 172.16.2.1 255.255.255.0
!
interface Vlan3
ip address 172.16.3.1 255.255.255.0
!
[output truncated]
!
Terry_3550#
The only other thing we need to do is make sure that the routing table is properly populated. By
default, IP routing is not enabled on a layer 3 switch, so we need to configure that with the global
command ip routing. After this is done, you can view the routing table in the normal way:
Terry_3550#
Terry_3550#conf t
Terry_3550(config)#ip routing
Terry_3550(config)#exit
Terry_3550#
Terry_3550#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 not set
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.1.0 is directly connected, Vlan1
C 172.16.2.0 is directly connected, Vlan2
C 172.16.3.0 is directly connected, Vlan3
Terry_3550#
Notice that the complete range of routing protocols is available for use. This
immensely powerful piece of equipment can be used for full multilayer switching
and routing as needed. So far we have not needed to configure a routing
protocol, as all of our subnets are directly attached, but as the internetwork
grows we shall undoubtedly need to configure dynamic routing.