IGRP and EIGRP

IGRP and EIGRP
THE CCNP EXAM TOPICS COVERED IN THIS
CHAPTER INCLUDE THE FOLLOWING:


Understand how EIGRP operates.


Understand how to configure EIGRP and verify proper
operation.


When route selection and configuration problems occur,
understand how to use the various show and debug
commands to determine the cause of the problem.
So far in this book, you have learned how routing protocols are
used to exchange IP address information between routers in an
enterprise network. IP addressing schemes establish a hierarchy
that makes path information both distinct and efficient. A router receives this routing information
via a given interface. It then advertises the information it knows to the other physical interfaces.
This routing process occurs at layer 3 of the OSI model. In this chapter, in order to decide on the
best routing protocol or protocols to use, we’ll take a look at both the Interior Gateway Routing
Protocol (IGRP) and its big brother, the Enhanced Interior Gateway Routing Protocol (EIGRP).
Unlike link-state routing protocols IS-IS and OSPF, IGRP and EIGRP are proprietary Cisco
protocols and run on Cisco routers and internal route processors found in the Cisco Distribution
and Core layer switches. (We need to note here that Cisco has licensed IGRP to be used on
other vendors’ equipment such as Compaq and Nokia.) Each of these routing protocols also has
its own identifiable functions, so we’ll discuss each routing protocol’s features and differences.
Once you understand how these protocols differ from OSPF and how they calculate routes, you
will learn how to configure these protocols and fine-tune them with configuration changes to
make each perform at peak efficiency.