Chapter 3. Introducing Switching, Routing, and Address Translation

Chapter Goals

This Chapter introduces the reader to TCP/IP routing and switching. The following topics are covered:

• Layer 2 SwitchingLearn how Ethernet frames are switched by LAN switches.

• Layer 3 RoutingLearn how IP packets are routed by routers.

• Layer 3 SwitchingLearn how IP packets are switched by routers.

• Layer 34 Network Address TranslationLearn how TCP segments and IP packets are translated by NAT-capable devices.

In Chapter 2, "Exploring the Network Layers," you learned how TCP segments, IP packets, and Ethernet frames are generated, encapsulated, and transmitted onto a network by TCP/IP devices.In this Chapter, you will learn how to design a network to efficiently translate, route, and switch the TCP segments, IP packets, and Ethernet frames that flow through your network. The following topics are discussed in this Chapter:

• Frame Switching and Virtual LANs Switching TCP/IP involves forwarding Layer 2 Ethernet frames within VLANs.

• IP Routing Static and dynamic routing protocols define the path that traffic takes from one end system to the other.

• Packet Switching Packets are switched within routers using process switching, fast switching, or Cisco Express Forwarding (CEF)

• Network Address Translation Packets' IP address fields are rewritten to conserve IP addresses, and hide internal IP addressing schemes and load balancing requests across groups of servers.