How does CEF differ from process switching?

Cisco Express Forwarding (CEF) is a highly optimized, hardware-based packet-forwarding mechanism that uses the Forwarding Information Base (FIB) and adjacency table to make forwarding decisions. The FIB is a copy of the routing table in a format optimized for fast lookups, and the adjacency table stores Layer 2 rewrite information. This allows CEF to forward packets quickly and efficiently without CPU involvement for each packet. In contrast, process switching is the slowest forwarding method, where every packet is sent to the router's main CPU for a full Layer 3 lookup, making it very CPU-intensive and inefficient for high-volume traffic. Therefore, process switching is significantly slower and more CPU-intensive than CEF, not faster or less CPU-intensive. CEF does not process "too complex" packets; it is the default and most efficient forwarding method for most traffic.