572 Appendix D: Comparisons of Dynamic Routing Protocols

RIP Version 2

RIP Version 2 (RIP-2), as currently defined in RFC 2453, defines several enhancements to the original RIP protocol, which is called RIP Version 1. (Chapter 5 covers RIP Version 1 details.) Like RIP-1, RIP-2 uses distance vector logic; uses hop count for the metric; sends full, periodic updates; and still converges relatively slowly.

RIP-2 does add support for VLSM, as compared with RIP-1, making it a classless routing protocol, with RIP-2 including the subnet mask for each subnet in the routing updates. Table D-2 outlines the improvements made to RIP with the creation of RIP-2.

Table D-2 Improvements Made to RIP by RIP V2

The most important feature comparing the two is that RIP-2 supports VLSM. Today, when choosing a routing protocol, RIP-1 would not be the best choice—in fact, the RIP- 1 RFC has been designated for historic status. Both protocols work well, but RIP-2 is more functional. If you want a routing protocol that uses a public standard and you want to avoid the complexity of link-state protocols, RIP-2 is your best choice today.

Routing Protocol Overview 573

The Integrated IS-IS Link State Routing Protocol

Once upon a time, the world of networking consisted of proprietary networking protocols from the various computer vendors. For companies that bought computers from only that one vendor, there was no problem. However, when you used multiple vendor’s computers, networking became more problematic.

One solution to the problem was the development of a standardized networking protocol, such as TCP/IP. Skipping a few dozen years of history, you get to today’s networking environment, where a computer vendor couldn’t sell a computer without it also supporting TCP/IP. Problem solved!

Well, before TCP/IP became the networking protocol standard solving all these problems, the International Organization for Standardization (ISO) worked hard on a set of protocols that together fit into an architecture called Open System Interconnection (OSI). OSI defined its own protocols for Layers 3 through 7, relying on other standards for Layers 1 and 2, much like TCP/IP does today. OSI did not become commercially viable, whereas TCP/IP did—the victory going to the nimbler, more flexible TCP/IP.

So, why bother telling you all this now? Well, OSI defines a network layer protocol called the Connectionless Network Protocol (CLNP). It also defines a routing protocol—a routing protocol used to advertise CLNP routes, called Intermediate System-to- Intermediate System (IS-IS). IS-IS advertises CLNP routes between “intermediate systems,” which is what OSI calls routers.

Later in life, IS-IS was updated to include the capability to advertise IP routes as well as CLNP routes. To distinguish it from the older IS-IS, this new updated IS-IS is called Integrated IS-IS. The word integrated identifies the fact that the routing protocol can exchange routing information for multiple Layer 3 routed protocols.

IS-IS and OSPF are Link State protocols. Link-state protocols prevent loops from occurring easily because each router essentially has a complete map of the network. If you take a trip in your car and you have a map, you are a lot less likely to get lost than someone else who is just reading the signs by the side of the road. Likewise, the detailed topological information helps link-state protocols easily avoid loops. As you will in chapter 5, the main reasons that distance vector protocols converge slowly are related to the loop-avoidance features. With link-state protocols, those same loop-avoidance features are not needed, allowing for fast convergence—often in less than 10 seconds.

574 Appendix D: Comparisons of Dynamic Routing Protocols

Integrated IS-IS has an advantage over OSPF because it supports both CLNP and IP route advertisement, but most installations could not care less about CLNP, so that advantage is minor. Table D-3 outlines the key comparison points with all Interior routing protocols for both Integrated IS-IS and OSPF.

Table D-3 IP Link-State Protocols Compared

Summary of Interior Routing Protocols

Before finishing your study for the INTRO or CCNA exam, you will learn a lot more about RIP-1, IGRP, EIGRP, and OSPF. This appendix has introduced you to some of the key terms and points of comparison for these routing protocols, as well covering a few details about other routing protocols. Table D-4 summarizes the most important points of comparison between the interior routing protocols, and Table D-5 lists some of the key terminology.

Table D-4 Interior IP Routing Protocols Compared: Summary

A P P E N D I X E

Configuring Cisco

1900 Switches

In years past, Cisco used the Catalyst 1900 switch line as the recommended switches in their courses relating to CCNA. The 1900 series is no longer a reasonable choice when purchasing a new switch from Cisco – in fact, you cannot even buy a new one any more. So, Cisco has added coverage of both 1900’s and 2950 series switches to their courses, so the Cisco Learning Partner teaching the course can effectively use an older lab, or update their labs and use the more modern 2950 switches. In the end, Cisco simply wants you to learn the types of things you configure on a switch – so using an older model can still be useful for learning.

We strive to ensure that all possible exam topics are included somewhere in these books, even the ones that may be less likely to be on the exams. So, while you’ll find lots of coverage of 2950’s in the main chapters, the 1900 coverage is relegated to this appendix. Simply put, the topics in this appendix could be covered on one of the exams, but the investment of study time in these topics may not be worth the return. For those of you who want to be super-prepared, this appendix lists some pertinent details about 1900 series switches.

Basic 1900 Switch Configuration

On the Catalyst 1900 switch, three different configuration methods exist:

■Menu-driven interface from the console port

■Web-based Visual Switch Manager (VSM)

■IOS command-line interface (CLI)

578 Appendix E: Configuring Cisco 1900 Switches

As mentioned earlier, this chapter focuses on using the CLI to configure the switch. Table E-1 lists the switch commands referred to in this section.

Table E-1 Commands for Catalyst 1900 Switch Configuration

Default 1900 Configuration

The default values vary depending on the features of the switch. The following list provides some of the default settings for the Catalyst 1900 switch. (Not all the defaults are shown in this example.)

■IP address: 0.0.0.0

■CDP: Enabled