7.2 Basic MLS Configuration
7.2.6 Assigning a VLAN ID to an interface on an external router
Multilayer switching uses inter-VLAN routing. Multilayer switches make forwarding decisions based upon which ports are configured for which VLANs. Internal Route Processors and ISL-configured links inherently use VLAN IDs to identify interfaces. External Route Processor interfaces have knowledge regarding subnets but not VLANs. Therefore, MLS requires that each external Route Processor interface have a VLAN ID assigned to it.

To assign a VLAN ID to a Route Processor interface, enter the following command in interface configuration mode:

Router(config)#interface interface number
Router(config-if)#mls rp vlan-id vlan-id-num

where vlan-id-num represents the VLAN assigned to this interface.

To remove an interface from a VLAN, enter the no mls rp vlan-id vlan-id-num command. Removing the VLAN ID from an interface disables MLS for that interface.