Module Summary CEF must be running as a prerequisite to running MPLS on a Cisco router. Frame-mode MPLS requires CEF switching and MPLS enabled on appropriate interfaces. Optional items include MPLS ID, MTU, IP TTL, and conditional label advertisement. When you encounter problems with frame-mode MPLS interfaces, it is helpful to know the procedures for monitoring MPLS on Cisco IOS platforms. When you verify correct operation of MPLS in the network, you will also need to know the recommended troubleshooting procedures. Lesson Aim <Enter lesson aim here.>