This paper presents an inter-FE topology discovery technology on ForCES router, it introduced a new type of topology discovery protocol ITDP (Inter-FE Topology Discovery Protocol). ITDP broadcast the prescribed format of the ITDP packets to each ITDP protocol port when FE is initialized, adjacent FE put these information into a neighbor table after the receipt of ITDP message packet, constructed FE topology. This article also researches the FE topology maintenance, use the FE heartbeat mechanism to achieve the maintenance.