Networks deploying hierarchical routing are recursively partitioned into sub-networks that do not reveal full details of their internal structure outside their domains. Instead, an aggregated view of certain parameters that are associated with traversal within such sub-networks between their border nodes is advertised. The ATM PNNI standard and the Internet Nimrod architecture both adopt this approach for routing. This paper studies the effectiveness of ATM hierarchical routing protocols on networks with different hierarchical structures by simulation. Our study shows that, in general, the hierarchical source routing performs well, compared to the global routing strategy which imposes no hierarchy, while utilizing less storage and communication overheads. For certain networks and topologies, the hierarchical routing performs better than the global routing. Different hierarchies imposed on the same topologies have significantly different performance on the throughput and routing delay. This suggests the necessity of studying the hierarchy design for communication networks using hierarchical routing.