In this paper, the performance of peer-to-peer (P2P) file sharing service based-on flooding search algorithm is analyzed. We focus on six types of four-terminal four-router physical network, and investigate the impact of topology inconsistency and flooding search on the file retrieval performance. The analysis model is based on a two-layer queueing network in which both logical and physical topologies are taken into account, and the file search time and file transfer delay are analyzed. We observe from numerical examples that an overlay network with high node degree provides a small file search time for a low traffic intensity, while the performance of the high node-degree overlay network rapidly degrades with a high traffic intensity.