This Chapter introduces the reader to many Layer 24 services available in Cisco routers, switches, firewalls, and content switches:
Layer 2 frame services Cisco Layer 2 switches perform MAC address learning in order to transparently switch MAC frames at Layer 2.
Layer 3 packet services Cisco IOS routers determine the path that packets take throughout a network using static or dynamic routing. Within the router, packets forwarded using process, fast, and CEF switching.
Layer 4 segment services Cisco IOS routers and firewalls perform network address translation to conserve registered IP addresses and hide internal IP addressing schemes. Cisco content switches perform destination address translation to distribute requests across identical servers in a server farm.