Hi,
Switching methods that routers use, define the way how pkts are handled by router. There are 3 methods:
Process Switching: legacy switching type. Each & evry pkt does a routing lookup to find reachability to destination, next-hop, & the interface from where next-hop is available.
Fast Switching: 1st pkt is process switched. Stores the info in a cache, thus reduce the router lookup time for following pkt to same destination. The cache info is timed out at regular intervals.
CEF: no process switching for 1st pkt. Router builds 2 tables, cef table that defines reachability of network, & adjacenccy table to define the next-hop & interface via which nxt-hop is reachable. Cache is not aged out.
