Читать книгу CCNP Enterprise Certification Study Guide: Implementing and Operating Cisco Enterprise Network Core Technologies - Ben Piper, David Higby Clinton - Страница 40

What's the difference between routing and forwarding? Not much, really. Forwarding is about sending the data one step closer to its destination. Routing is about figuring out what that next step is.

The routing versus forwarding distinction has nothing to do with layers. Recall that switches perform a crude version of routing by snooping the data plane to find out which port a MAC address is connected to. They compile this into a MAC address table, which they use to make forwarding decisions.

When it comes to IP, route calculation and route advertisements are performed by interior gateway routing protocols such as Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF). Although we don't normally think of them in this way, routing protocols are actually applications that run on routers. They just populate the IP routing table that feeds into the FIB, but CEF does the forwarding.