Forwarding Architectures

In the beginning Cisco routers on recieving a packet would remove the Layer 2 information and verify that the route existed for the destination address on that packet. If a matching route could not be found on the router, the packet would be dropped. Otherwise if a matching route was found, new Layer 2 information would be added to the packet and forwarded. This was called process switching.

As Cisco router technology has advanced the routers no longer remove the addressing but simply rewrite it. IP packet switching or packet forwarding is a faster process than waiting to recieve a packet, read it, and determine whether it needs to be dropped or forwarded. This became knoiwn as fast switching and later Cisco Express Forwarding (CEF)