To ensure high availability of telephone services, there is considerable interest in network management activities to develop competent fault management mechanisms. In this paper we investigate, examine, and try to adapt the current active probing technologies to fault isolation and problem determination of telecommunication networks. The unfitness, issues, and difficulties while adopting these IP-networking probing methods into fault isolation of telecommunication networks are addressed and elaborated. For achieving our goal, call-forwarding which is a dedicated function (or feature) in telecommunication networks is utilized to overcome the unfitness and difficulties while applying probing technologies to fault isolation of telecommunication networks. Numerous experiments with different probe sets, probe stations, total probe lengths, network topologies, and probing algorithms are conducted and analyzed to validate our strategy. From the results of our experiments, we can find that phone call-forwarding can not only facilitate the fault isolation with the existing active probing techniques, but also increase the system flexibility on the installation of probe stations. Meanwhile, on the basis of our experimental results, several practical suggestions are also provided for system implementation.