At 4:25 PM -0400 5/13/02, Logan, Harold wrote: >You're right about IGRP still being listed on the CCNA objectives. While >I've sometimes found it frustrating to teach an outdated protocol, IGRP is >useful as a teaching tool. With IGRP you can easily demonstrate the concept >of composite metrics, poison reverse, holddown timers, split horizon, and >unequal-cost load balancing, but you don't have multicast updates, neighbor >relationships, incremental updates, and VLSM's adding to the confusion.
You make some interesting instructional points that I want to think about. Let me make some observations. No modern routing protocol uses composite metrics, in the sense that a numerical value is computed from several factors. I don't know if you'd consider route preference (e.g., OSPF intraarea over interarea over external) to be composite; I don't. Poison reverse, split horizon and holddown are explained decently in the very readable RIP RFC. Unequal cost load balancing is increasingly deprecated; there are better ways to do traffic engineering. > >If EIGRP replaces IGRP on the CCNA, then hopefully the certification team >will draw a clear line indicating which features of eigrp will be tested and >which ones won't. The way things are right now, IGRP makes for a smooth >transition from the CCNA to the CCNP Routing exam. Someone who understands >IGRP doesn't need to reinvent the wheel to learn EIGRP, I'd argue that other than some similarities in commands and metrics, IGRP and EIGRP are completely different protocols. There is a trivial case of neighbor relationships in RIP, as a router with a RIP-enabled interface will suppress outgoing updates until it hears a RIP query from a router on the medium. That is a form of neighbor discovery. It is different from using a hello subprotocol to know if a neighbor is still alive. Personally, when I'm teaching beginning IP, I start with binary, and then VLSM/CIDR becomes a natural idea. I then introduce dotted decimal, and only as an afterthought mention classes. Works well whenever I've tried it. >and once one has >supernetting and neighbor relationships in his or her belt, they can deal >with OSPF area types and LSA's and the like. > >Hal Logan CCAI, CCDP, CCNP:Voice >Network Specialist / Adjunct Faculty >Computing & Engineering Technology >Manatee Community College -- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** ******************************************************************************** Howard C. Berkowitz [EMAIL PROTECTED] Chief Technology Officer, GettLab/Gett Communications http://www.gettlabs.com Technical Director, CertificationZone.com http://www.certificationzone.com "retired" Certified Cisco Systems Instructor (CID) #93005 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44200&t=43994 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
