Editing Hierarchical routing

{{Short description|Network routing based on hierarchical addressing}}
'''Hierarchical routing'''  is a method of [[routing]] in networks that is based on hierarchical [[network address|addressing]].

==Background==
Most [[Transmission Control Protocol]]/[[Internet Protocol]] ([[Internet protocol suite|TCP/IP]]) routing is based on a two-level hierarchical routing in which an IP [[Network address|address]] is divided into a [[computer network|network]] portion and a [[Server (computing)|host]] portion. Gateways use only the network portion until an IP [[datagram]] reaches a [[Gateway (computer networking)|gateway]] that can deliver it directly. Additional levels of hierarchical routing are introduced by the addition of subnetworks.

==Description==
Hierarchical routing is the procedure of arranging [[router (computing)|router]]s in a hierarchical manner. A good example would be to consider a corporate [[intranet]]. 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 [[local area network|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.

Considering alternative solutions with every router connected to every other router, or if every router was connected to 2 routers, shows the convenience of hierarchical routing. It decreases the complexity of [[network topology]], increases routing efficiency, and causes much less [[Network congestion|congestion]] because of fewer routing advertisements. With hierarchical routing, only core routers connected to the backbone are aware of all routes. Routers that lie within a LAN only know about routes in the LAN. Unrecognized destinations are passed to the default route.

==References==
*{{FS1037C}}

==External links==
*[http://www.isi.edu/nsnam/ns/doc-stable/node310.html http://www.isi.edu/nsnam/ns/doc-stable/node310.html]

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[[Category:Routing]]