CEF - Operation within a chassis switch

Because the architecture of a chassis switch is a little bit different than a non-modular switch, you have two types of CEF.

We have centralized CEF, which uses the intelligence in the RSP cards to perform CEF. Remember, the RSP is not just a CPU, but it is all of the circuitry (CPU, memory, ASICs, CAM/TCAM, and other high-speed hardware) required by a switch.

On the other hand Distributed CEF bypasses the RSP by using hardware that is built-in on board each line card. In other words, some intelligence and high speed hardware is included in the line cards themselves. This further speeds up the CEF process since it bypasses the route processor.

You must think about a chassis switch in the same way as a non-modular switch, except that the various components of the switch are separated onto different components (line cards and supervisor engines) for the purpose of modularity. The special case of distributed and centralized CEF is simply because of this distinction between these components.