the big difference...
process switching requires cpu involvement with every forwarding decision
fast switching relies on the cpu as well but once a packet is forwarded,
the destination path is stored in fast switching cache. this allows the
path to be re-used from the cache and precludes a new look up by the cpu
for that path
cef is the next evolution enabling the router to forward packets yet
faster. it builds a forward information base and an adjacency table.
access is quick because it is bulit into the hardware (asics). the fib contains
pre-computed reverse lookups as well as next hops, and layer 2
information and the interface to use.
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