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The Illustrated Network- P40

The Illustrated Network- P40:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER 14 IGPs RIP OSPF and IS-IS 359 Limited Metrics As a network grows the distance-vector might require a metric greater than 15 which is unreachable infinite . No Link Speed Allowances The simple hop count metric will always result in packets being sent as an example over two hops using low-speed 64-kbps links rather than three hops using SONET SDH links. No Authentication RIPvl devices will accept RIPvl updates from any other device. Hackers love RIPvl for this very reason but even an innocently misconfigured router can disrupt an entire network using RIPv1. Subnet Masks RIPvl requires the use of the same subnet mask because RIPvl updates do not carry any subnet mask information. Slow Convergence Convergence can be very slow with RIPvl often 5 minutes or more when links result in long chains of routers instead of neat meshes. And circles of RIPvl routers maximize the risk of counting to infinity. RIPv2 RIPv2 first emerged as an update to RIPvl in RFC l388 issued in January l993. This initial RFC was superseded by RFC l723 in November l994. The only real difference between RFC l388 and RFC l723 is that RFC l723 deleted a 2-byte Domain field from the RIPv2 packet format designating this space as unused. No one was really sure how to use the Domain field anyway. The current RIPv2 RFC is RFC 2453 from November l998. RIPv2 was not intended as a replacement for RIPvl but to extend the functions of RIPvl and make RIP more suitable for VLSM. The RIP message format was changed as well to allow for authentication and multicasting. In spite of the changes RIPv2 is still RIP and suffers from many of the same limitations as RIPvl. Most router vendors support RIPv2 by default but allow interfaces or whole routers to be configured for backward compatibility with RIPvl. RIPv2 made major improvements to RIPvl Authentication between RIP routers Subnet masks to be sent along with routes Next hop IP addresses to be sent along with routes Multicasting of RIPv2 messages The RIPv2