The forwarding enging, which handles the incoming frames and forwards them to the appropriate outgoing interface, is the crucial factor of the router´s performance. As the MPLS label edge router provides the facility that it is capable of interworking with various kinds of networks, the forwarding engine should have the flexibility processing the corresponding types of frames from such network interfaces. In order to support the flexibility, we implement the forwarding engine for the MPLS LER with ATM interfaces based on the programmable Ethernet packet processor. By exploiting instinct loop-back functionality of Ethernet packet processor, our forwarding engine handles and forwards the frames from/to ATM interfaces. The performance of our forwarding engine is evaluated by experiments on the effect of looping frames back and the number of Ethernet packet processor´s instructions.