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| 4.2 |  | Configuring Inter-VLAN Routing |
| 4.2.4 |  | Configuring routing between an external router and an internal route processor |

It is often necessary to connect an external router to an internal route switch processor. A common reason for this is to provide access to a WAN interface as these are often not provided on a switch.

The easiest method of implementing this is to create a routed port.

> RouteSwitch(config)#interface fa 0/1
> RouteSwitch(config-if)#no switchport
> RouteSwitch(config-if)#ip address 10.0.1.1 255.255.255.0

> ExtRouter(config)#interface fa 0/0
> ExtRouter(config-if)#ip address 10.0.1.2 255.255.255.0

Although a routed port is configured for connectivity with an external router, Inter-VLAN routing would most likely be achieved through the use of a virtual interface.

To route between VLANs 10 and 20 which have been configured on the multilayer switch use the following configuration:

> RouteSwitch(config)#interface vlan 10
> RouteSwitch(config-if)#ip address 10.0.10.1 255.255.255.0
> RouteSwitch(config)#interface vlan 20
> RouteSwitch(config-if)#ip address 10.0.20.1 255.255.255.0

It is also likely that the internal route processor on the switch will need to run a dynamic routing protocol and perhaps include some static routes.

> RouteSwitch(config)#router ospf 10
> RouteSwitch(config-router)#network 172.16.0.0 0.0.255.255 area 0