Abstract: Knowledge of the up-to-date physical Ethernet network topology is crucial to a number of import network management tasks, including network resource management, root-cause analysis, event correlation. Thus, effective and universal algorithms for automatically discovering physical network topology are very necessary. In this paper, we investigate the problem of the physical topology of large, heterogeneous multi-subnet that may include multi-vendor, uncooperative network elements. Then, we present a novel and effective algorithm for automatically discovering physical network topology in heterogeneous multi-subnet. Our approach utilizes only generic standard SNMP MIB information and does not require any modifications for the network elements and the operating system. The experimental results prove the correctness of the algorithm and the sufficient and necessary conditions for the uniqueness of the restored topology and demonstrate that our tool can automatically discover the accurate physical network topology even for large, heterogeneous network configurations.