Fast switching uses a fast-switching cache to store next-hop information
When a packet arrives on an interface, it is forwarded to the control plane where the CPU searches for a match in the fast-switching cache
If it is not there, it is process-switched and forwarded to the exit interface
The flow information for the packet is then stored in the fast-switching cache
If another packet going to the same destination arrives on an interface, the next-hop information in the cache is re-used without CPU intervention