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| 5.3 |  | MLS and CEF Configuration Tasks |
| 5.3.1 |  | MLS-RP configuration |

Configuring MLS support on an MLS-RP has five basic steps, which are detailed in the following list. After detailing the configuration steps for an MLS-RP and an MLS-SE, a complete example will follow.

Step 1
The first step is to configure the MLS-RP to globally enable MLS. This is analogous to enabling IPX or multicast routing on a router. The global configuration Cisco IOS Software command to enable MLS is mls rp ip. A Catalyst 6000 with Supervisor Engine I and an MSFC has IP MLS globally enabled by default.

Step 2
Determine which router interfaces will use as IP MLS interfaces, and add those interfaces to the same VTP domain as the MLS-SE. Remember that router interfaces will be VLAN interfaces (not physical interfaces) on the RSM, RSFC, and MSFC. The complete syntax for the command to add an IP MLS interface to a VTP domain is mls rp vtp-domain [domain_name].

On ISL or 802.1Q trunks, enter the mls rp vtp-domain command on the primary interface (not on the individual subinterfaces). All subinterfaces on the primary interface inherit the VTP domain assigned to the primary interface. The command mls rp vtp-domain is also used on physical interfaces configured as access ports (ports with only one VLAN association). On the RSFC, RSM, and MSFC, this command is entered on each VLAN interface participating in MLS.

Step 3
For Layer 3 interfaces that are not trunk ports and IP MLS support is desired, start by verifying that the interface has been assigned to a VLAN (as an access port). Then assign a VLAN ID to the IP MLS interface with the interface command mls rp vlan-id [vlan_id_num].

Step 4
Enable IP MLS on the interfaces participating in IP MLS with the command mls rp ip. This is the same command used in global configuration mode, but here it is applied at the interface level. In the case of an ISL or 802.1Q trunk, this command must be configured on all subinterfaces (it is not entered on the physical interface itself). On the MSFC, RSM, and RSFC, this command is entered on VLAN interfaces.

Step 5
Specify an MLS-RP interface as an MLS-RP management interface. MLSP runs on the management interface, sending hello messages, advertising routing changes, and announcing VLANs and MAC addresses of interfaces participating in MLS. At least one router interface must be configured as a management interface (more than one is permitted, but this introduces a proportional increase in overhead). If a management interface is not specified, IP MLS will not function.

Also, the MLS-SE must have an active port in at least one VLAN that has a corresponding router interface configured as a management interface. The interface command to specify an MLS-RP interface as a management interface is mls rp management-interface. In the case of an ISL or 802.1Q trunk, this command is applied to a particular subinterface (not to the interface itself).

Finally, configuring output ACLs on MLS-RP interfaces works seamlessly with MLS, meaning that MLS cache entries are created that reflect the desired behavior of the ACL while still providing wire-speed switching of packets. On the other hand, input ACLs on MLS-RP interfaces force every packet to be routed by the MLS-RP.

To enable MLS to cooperate with input ACL, enter the global configuration command mls rp ip input-acl.