7.2 Basic MLS Configuration
7.2.3 Enabling MLS on an interface
Putting an MLS interface into a VTP domain does not activate MLS on the interface. MLS must be explicitly entered on the interface. Because of the one-to-one relationship between VLANs and subnets, each interface that is to participate in Layer 3 switching must be enabled for multilayer switching.

To enable an RSM interface for multilayer switching, enter the following command in interface configuration mode.

Router(config-if)#mls rp ip

The running configuration example in the Figure states that the VLAN41 interface of the MLS-RP is enabled to participate in multilayer switching.

To disable multilayer switching on an interface, enter the no mls rp ip command.