CCNP Routing Study Guide- P9

CCNP Routing Study Guide- P9:T his book is intended to help you continue on your exciting new path toward obtaining your CCNP and CCIE certification. Before reading this book, it is important to have at least read the Sybex CCNA: Cisco Certified Network Associate Study Guide, Second Edition. You can take the CCNP tests in any order, but you should have passed the CCNA exam before pursuing your CCNP.
Nội dung trích xuất từ tài liệu:
CCNP Routing Study Guide- P9 Chapter IGRP and EIGRP 6 THE CCNP ROUTING EXAM TOPICS COVERED IN THIS CHAPTER ARE AS FOLLOWS: Describe IGRP features and operation Configure IGRP Verify IGRP operation Describe Enhanced IGRP features and operation Explain how metrics are used with EIGRP Explain how DUAL is used with EIGRP Explain the features supported by EIGRP Learn how EIGRP discovers, decides, and maintains routes Explain EIGRP process identifiers Explain EIGRP troubleshooting commands Configure EIGRP and verify its operation Verify route redistribution Copyright ©2001 SYBEX , Inc., Alameda, CA www.sybex.com S o far in this book, we have taken an in-depth look at the rout- ing protocol OSPF and shown how a routing protocol is used to find routes through the network. We also 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 out 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 Pro- tocol (EIGRP). Unlike OSPF, IGRP and EIGRP are proprietary Cisco protocols and run on Cisco routers and internal route processors found in the Cisco Distribu- tion and Core layer switches. (I need to note here that Cisco has licensed IGRP to be used on other vendors’ equipment, such as Compaq.) Each of these routing protocols also has its own identifiable functions, so we’ll dis- cuss 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 config- uration changes to make each perform at peak efficiency. Copyright ©2001 SYBEX , Inc., Alameda, CA www.sybex.com Scalability Features of Routing Protocols 205 Scalability Features of Routing Protocols Several times in this book, as we look at the different routing proto- cols—OSPF, IGRP, EIGRP, and BGP—we will refer back to distance-vector and link-state routing protocol differences. It is important to identify how these protocols differ from one another. As networks grow and administrators implement or use Cisco-powered networks, OSPF might not be the most efficient or recommended protocol to use. OSPF does have some advantages of IGRP, EIGRP, and BGP, including: It is versatile. It uses a very scalable routing algorithm. It allows the use of a routing protocol that is compatible with non- Cisco routers. BGP will be discussed in Chapters 7 through 9. Cisco provides two other proprietary solutions that allow better scaling and convergence, which can be very critical issues. These are the Interior Gateway Routing Protocol (IGRP) and Enhanced IGRP (EIGRP). Network growth imposes a great number of changes on the network environment and takes into consideration the following factors: The number of hops between end systems The number of routes in the routing table The different ways a route was learned Route convergence IGRP and EIGRP can be used to maintain a very stable routing environment, which is absolutely crucial in larger networks. As the effects of network growth start to manifest themselves, whether or not your network’s routers can meet the challenges faced in a larger scaled network is completely up to the routing protocol the routers are running. If you use a protocol that’s limited by the number of hops it can traverse, the Copyright ©2001 SYBEX , Inc., Alameda, CA www.sybex.com 206 Chapter 6 IGRP and EIGRP number of routes it can store in its table, or even the inability to communi- cate with other protocols, then you have a protocol that will likely hinder the growth of your network. All the issues we’ve brought up so far are general scalability consider- ations. Before we look at IGRP and EIGRP, let’s take another look at the dif- ferences between link-state routing protocols and distance-vector protocols and the scalability issues of each. Link-state routing and distance-vector protocols are discussed in detail in Chapter 2, and are discussed in Chapter 7 as they relate to BGP. Distance-Vector Protocol Scalability Issues In small networks—meaning those with fewer than 100 routers and an envi- ronment that’s much more forgiving of routing updates and calculations— distance-vector protocols perform fairly wel ...