Selected Answer: AD CEF can be enabled in one of two modes: Central CEF mode - When CEF mode is enabled, the CEF FIB and adjacency tables reside on the route processor, and the route processor does the express forwarding. You can use CEF mode when line cards are not available for CEF switching, or when you need to use features not compatible with distributed CEF switching. Distributed CEF (dCEF) mode - When dCEF is enabled, line cards keep identical copies of the FIB and adjacency tables. The line cards can do the express forwarding on their own, and this relieves the main processor - Gigabit Route Processor (GRP) - from involvement in the switching operation. This is the only switching method available on the Cisco 12000 Series Router. https://www.cisco.com/c/en/us/support/docs/routers/12000-series-routers/47321-ciscoef.html

Great explanation, thank you!