Chapter 10

Forwarding IP Packets


In this chapter, you will learn how routers forward IP packets. We’ll start with the logical steps a router follows to forward (“route”) a packet out the next-hop interface. Then we’ll look at router architectures to see how specialized devices (there are “software-only” routers) accomplish routing and forwarding.

Finally, you will learn about how IPv4 routers transition to handling IPv6 routing and various methods to tunnel IPv6 packets through links connected by IPv4-only routers. Tunnels were introduced in Chapters 3 and 4 and occur when the normal encapsulation sequence of packet–inside frame is violated in some fashion.


Router architecture; tunneling; ICMP; TTL; DNS; LANs; NVRAM; CPU chips; ...

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