We propose centralized server based QoS routing schemes, where a route server is responsible for determining QoS paths on behalf of all the routers in the routing domain. In the proposed server based schemes, the dynamic link QoS state information, which is required for a QoS path computation, is implicitly maintained at the route server as it assigns or retrieves QoS paths. By maintaining the network state information this way, we may not only eliminate the overhead in exchanging network state update messages but also achieve higher routing performance. We discuss techniques for reducing the amount of processing overhead at the route server, and evaluate the performance of the proposed schemes using simulation. The simulation results show that the proposed server based QoS routing schemes may improve the routing performance compared to the distributed QoS routing schemes proposed in the literature, and the proposed processing reduction methods may significantly reduce the processing cost at the route server.