What is a Routing Table?
A Routing Table is an electronic document that stores the routes to the various nodes in a computer network. The nodes may be any kind of electronic device connected to the network. The Routing Table is usually stored in a router or networked computer in the form of a database or file. When data needs to be sent from one node to another on the network, the routing table is referred to in order to find the best possible route for the transfer of information.
Hop-by-hop Routing is a common routing method used in networks wherein for each node in the network, the address of the next node leading to the destination is listed. So when a data packet arrives at a particular node, it then refers to the routing table to find the address of the next hop destination. Once it reaches that node, it again refers to the routing table for the address of the next hop and so on, until it reaches the final destination.
For a large network consisting of a number of nodes and routers, the routing tables in all the routers need to be consistent, failing which, routing loops can often develop. This can create problems especially in networks that use the hop-by-hop routing model in which the data packets can end up being sent in an endless loop. Routing loops have always been a recurring problem in networks and one of the major goals of designing routing protocols is the careful avoidance of these routing loops.
Routing tables can generally be maintained manually when the network is small and static. The routing tables for all static network devices never change unless and until the administrator of the network changes them manually. In dynamic routing, the devices themselves automatically build and maintain their own routing tables. They do this by exchanging information regarding the network topology using routing protocols. This enables the devices in the network to automatically adapt to the changes in the network like device failures and network congestion as and when they occur.
Books on Routing
 Routing TCP/IP Volume I |
This all-encompassing TCP/IP text defines completeness with its one-thousand-plus pages and hundreds of configuration screens, exercises, charts, tables, and references. Though initially overwhelming, such thoroughness is what's demanded of those who ultimately pass the Cisco Certified Internetwork Expert (CCIE) exam, the bruising test for which Routing TCP/IP, Volume 1 serves as preparatory material.
Such a goal is evidenced in much of the three-part book's design. For example, nearly every chapter includes some combination of recommended readings, review questions, configuration and troubleshooting exercises, case studies, and summaries. In addition, there are numerous appendices devoted to answers to questions and exercise solutions as well as one that outlines exam preparation tips. Doyle begins this volume with a review of several basic topics, including a chapter that outlines the parameters of TCP/IP itself. Though some may already be familiar with that material, the sections on dynamic and static routing serve as valuable review material for readers of all levels. The second part deals with TCP/IP interior routing protocols, such as Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), and Open Shortest Path First (OSPF). The book ends on a challenging note with explanations of route redistribution, route filtering, and the like. Routing TCP/IP is required reading for those readers with the ambitious goal to both understand the protocol and excel on the CCIE exam. |
 IP Routing Fundamentals | A comprehensive ntroduction to routing concepts and protocols in IP networks.Comprehensive review of the operational mechanics of today's leading routing protocols, including IGRP, EIGRP, OSPF, RIP, and RIP-2. Detailed explanation of IP addressing, including classful and classless addresses, subnetting, supernetting, Classless Interdomain Routing (CIDR), and Variable Length Subnet Masks (VLSM). Side-by-side comparisons of various LAN segmentation technologies, including bridges, switches, and routersExploration of how routers are used to build wide area networksExamination of the future of routing, including IPv6, next generation routing protocols, host-based routing, and IP SwitchingIP Routing Fundamentals is the definitive introduction to routing in IP networks. This comprehensive tome explores the mechanics of routers, routing protocols, network interfaces, and operating systems. This reference provides essential background information for network professionals who are deploying and maintaining LANs and WANs, as well as IT managers who are seeking information on how evolving internetworking technology will affect future networks. Part I discusses the many roles routers play in networks, Part II talks about the inner working of routers, Part III works with the operational issues of routing protocols, and Part IV addresses implementation issues that provide practical insight, in addition to a discussion of the future of routing. |
 Teach Yourself Routing in 24 Hours | Learn routing in the most efficient, enjoyable way possible with Sams Teach Yourself Routing in 24 Hours. Book presents routing concepts in a vendor-neutral presentation. The book is full of insight from the author's extensive knowledge and experience. Each lesson is designed to build upon previous lessons, but many can be read separately, thus providing the reader with a tutorial for routing basics as well as a means of learning about a particular routing concept quickly. Sams Teach Yourself Routing in 24 Hours presents routing fundamentals in twenty-four easy to follow lessons that build upon the previous lessons. Each of these lessons could stand alone as a tutorial on a particular routing concept thereby adding greater value to the book. In additional to these "easy to follow" lessons, this book is full of useful notes, tips, and cautions from the author's extensive experience that will prove invaluable to anyone who wants to learn routing as quickly as possible. The reader will also benefit from the exercises (each one based on an actual experience the author has encountered) at the end of each chapter. |
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