The paper describes a transmutable telecom system called ATTRACTOR, which uses more than 100 FPGAs, and features both reconfigurability and high performance. There are two key innovations. One is the board-level modularity concept that allows different functions to be implemented on different boards individually. The other is a high-speed serial link mechanism that provides excellent inter-board communication without sacrificing performance. Thus this system can be completely reconstructed to suit different applications by arranging different board combinations and reconfiguring each board. Using ATTRACTOR, we realized an IP packet forwarder, which is very speed-intensive telecom function, that has to decide the next-hop address of each incoming IP packet and send it out on-the-fly. It was confirmed that the function works well in a real ATM-LAN environment.