Multiprotocol-over-ATM (MPOA) is a service which supports layer-3 internetworking for hosts attached to ELANs (running a LAN Emulation Client-LEC), hosts attached to ATM networks, and hosts attached to legacy LANs. MPOA provides and delivers the functions of a router and takes advantage of the underlying ATM network as much as possible. That means, MPOA works as a virtual router with real QoS features of ATM. Furthermore, the integration of existing network with reduced protocol overhead and reduced equipment is a crucial point in terms of network performance cost efficiency. But MPOA has already some disadvantages, because MPOA is a very complex technology and the success of MPOA is doubtful. IP might be worth the complexity because it is so widely used, but it can be doubted if this holds true for other layer 3 protocols as well. Nevertheless, the MPOA model is a very promising technology which has also negative aspects like very complex software implementation (hard to handle) and QoS can only be supported if you use ATM network interface cards (NICs) directly without Ethernet. This paper will discuss the measurement results (latency, throughput) from the Internet Protocol (IP) in ATM and Ethernet environment via MPOA. Furthermore this paper will give an overview about available ATM components regarding MPOA and the further development of this technology.