An improved physical topology discovery algorithm for multi-subnet network

Based on the generic addresses forwarding table (AFT), a physical topology discovery algorithm, which is adaptable to multi-subnet network with shared segment and dump switch, is defined and the correctness is proved. The algorithm solves the problem that a complete AFT uniquely determines the physical topology for multi-subnet network, can discover the physical connections between switch and switch , switch and hub, switch and hub, switch and host ,host and hub. The example further proves the correctness of the algorithm.