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Types of Dynamic Routing Protocols 185
Figure 6-2
Static Route to a Stub Network
Types of Dynamic Routing Protocols
There are three categories of dynamic routing protocols:
·
Distance-vector
·
Link-state
·
Hybrids
They are covered in the following sections.
Distance-Vector Routing
In distance-vector routing, routers pass copies of their routing tables to their immediate network
neighbors at periodic intervals. Each recipient adds a distance vector, sometimes a hop count,
to the table and forwards it to its immediate neighbors. This process results in each router's
learning about other routers. For the most part, distance-vector protocols are simple protocols
that are easy to configure, maintain, and use. They are quite useful in very small networks that
have few redundant paths and no stringent network performance requirements. Distance-vector
protocols are not recommended for larger networks because of their slow convergence time and
limited diameter. RIP and IGRP are examples of distance-vector protocols.
Link-State Routing
Link-state routing algorithms, also known as shortest path first (SPF) protocols, maintain a
complex database of the network's topology. Link-state protocols develop and maintain a full
knowledge of the network's routers, as well as how they interconnect. Link-state routing uses
events such as change to drive updates instead of sending intervals at fixed times. Link-state
Corporate internetwork
Static route
One path
Default route
Stub
87200333.book Page 185 Wednesday, August 22, 2001 2:37 PM