Summary
The fundamental roles of routers are route-computation, packet scheduling, and forwarding. Router architecture has evolved through three generations, from a shared bus central CPU, to multiple peer-line cards connected by an intelligent switching fabric. With this evolution, the Cisco core product line has evolved from central CPU-orientated process switching through the use of a fast switching cache, to distributed CEF.
Routers may compute multiple RIBs, each associated with a particular routing protocol (OSPF, Enhanced IGRP, RIP, BGP, or IS-IS) or process. Similarly, routers also may contain multiple FIBs, each associated with a particular switching path (process, fast, CEF, or TAG). Improvement in route-lookup methodology, together ...
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