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n this chapter, you will learn the difference between distance-
vector and link-state routing protocols. The idea of this chapter is to provide
you with an overview of the different types of routing protocols available,
not how to configure routers. Distance-vector protocols will be covered in
more detail in this chapter than link-state because link-state routing proto-
cols are covered very thoroughly starting at Chapter 4, "OSPF Areas."
This is an important chapter to understand before moving on to the link-
state routing protocol chapters. Having a fundamental understanding of the
distance-vector and link-state concepts is important, as it will help you when
you design internetworks and the routing protocol implementation.
Fundamentals of Routing
outing is the process of forwarding packets from one network to
another; this is sometimes referred to as a relay system. Logical addressing is
used to identify each network as well as each device on the network. The
actual movement of transient traffic through the router is a separate func-
tion; it is actually considered to be the switching function. Routing devices
must perform both a routing and a switching function to be effective.
For a routing decision to take place on a relay system, three major deci-
sions must be made:
Is the logical destination address a known protocol? Is this protocol
enabled on the router and active? This does not have to be IP; IPX,
AppleTalk, and other protocol suites can be used as well.
Copyright ©2001 SYBEX , Inc., Alameda, CA