<P> Hierarchical routing is a method of routing in networks that is based on hierarchical addressing . </P> <P> Most Transmission Control Protocol / Internet Protocol (TCP / IP) routing is based on a two - level hierarchical routing in which an IP address is divided into a network portion and a host portion . Gateways use only the network portion until an IP datagram reaches a gateway that can deliver it directly . Additional levels of hierarchical routing are introduced by the addition of subnetworks . </P> <P> Hierarchical routing is the procedure of arranging routers in a hierarchical manner . A good example would be to consider a corporate (internet). Most corporate intranets consist of a high speed backbone network . Connected to this backbone are routers which are in turn connected to a particular workgroup . These workgroups occupy a unique LAN . The reason this is a good arrangement is because even though there might be dozens of different workgroups, the span (maximum hop count to get from one host to any other host on the network) is 2 . Even if the workgroups divided their LAN network into smaller partitions, the span could only increase to 4 in this particular example . </P>

What is the advantage of hierarchical routing versus flat routing