Cisco Express Forwarding
Cisco Express Forwarding (CEF) is a Cisco proprietary switching mechanism developed to keep up with the demands of evolving network infrastructures. It has been the default switching mechanism on most Cisco platforms that do all their packet switching using the general-purpose CPU (software based routers) since the 1990s, and it is the default switching mechanism used by all Cisco platforms that use specialized application specific integrated circuits (ASICs) and network processing units (NPUs) for high packet throughput (hardware-based routers).
The general-purpose CPU on the software-based and hardware-based routers is similar and perform all the same functions, the difference being that on software based routers the general-purpose CPU is in charge of all operations, including CEF switching (software CEF), and the hardware-based routers do CEF switching using forwarding engines that are implemented in specialized ASICs, TCAMs, and NPUs (hardware CEF). Forwarding engines provide the packet switching, forwarding, and route lookup capability to routers.
