Building an Initial Spanning Tree

Each bridge begins by claiming to be the root bridge. The Spanning-Tree Protocol defines messages used to exchange information with other bridges. These messages are called Configuration Bridge Protocol Data Units (CBPDUs). Each bridge begins by sending a CBPDU stating the following The root bridge's bridge ID. This is typically a MAC address on one of the bridge's interfaces. Each bridge sets this value to its own bridge ID. An administratively set priority. The cost between the bridge sending...

Scenario 54 IPX Examination

Given the network in Figure 5-46 and the command output in Example 5-29, Example 5-30, and Example 5-31, answer the questions and perform the tasks listed after Example 5-31. Figure 5-46 Scenario 5-4 Network Diagram Example 5-29 Albuquerque Command Output, Scenario 5-4 Albuquerque show ipx interface brief Albuquerque show cdp neighbor detail Example 5-29 Albuquerque Command Output, Scenario 5-4 (Continued) Platform cisco 2500, Capabilities Router Interface Serial0, Port ID (outgoing port)...

Network Protocols

TCP IP is the most important protocol covered on the CCNA exam and is the protocol used most often in networks today. This chapter covers the TCP IP protocols as well as IP addressing and subnetting. Cisco expects CCNAs not just to know IP addressing and routing, but also to know the concepts behind many other TCP IP protocols. In addition, CCNAs should be able to easily recall the commands used to examine the details of IP processing in a router. Of course, Cisco also requires you to...

Destination Unreachable ICMP Message

The five separate unreachable functions (codes) are accomplished using this single ICMP unreachable message. All five code types pertain directly to some IP, TCP, or UDP feature and are better described by using Figure 5-13 as an example network. Assume that Fred is trying to connect to the Web server, which uses TCP as the transport layer protocol. Three of the ICMP unreachable codes would possibly be used by Routers A and B. The other two codes would be used by the Web server. These ICMP...

Given a Network Number and a Static Subnet Mask How Many Hosts per Subnet and How Many Subnets

Finally, one more way the exam is likely to test your knowledge of IP addressing and subnetting is to ask which subnet masks will meet a set of requirements. This last type of question would be phrased as something like, If you need at least 30 hosts in each subnet and only 4 subnets, and if you are using network 192.1.1.0, which of the following masks meet your requirements To answer these types of questions confidently, you must have a good understanding of the three parts of an IP address....

Answers to Task 3 for Scenario

Task 3 for Scenario 6-1 asks for static route configuration. The routes to allow users on LANs to reach each other are shown in upcoming examples. However, routes to the subnets on serial links are not shown in these examples for brevity's sake the users should not need to send packets to IP addresses on the serial links' subnets, but rather to other hosts on the LANs. Example 6-33, Example 6-34, and Example 6-35 show the configurations on the three routers. Example 6-33 Albuquerque...

Table of Contents

Chapter 1 All About the Cisco Certified Network Associate Certification 2 How This Book Can Help You Prepare and Pass the CCNA Exam 4 Overview of Cisco Certifications 4 Exams Required for Certification 6 Other Cisco Certifications 7 Recommended Training Path for CCNA 11 How to Use This Book to Pass the Exam 12 I've Taken ICND Now What 14 I've Taken ICRC Now What 15 I've Taken the Cisco Networking Academy Courses Now What 16 I'm New to Internetworking with Cisco, and I Will Not Be Taking the...

IP Naming Commands and Telnet

Names are never important to the process of routing IP packets. However, most human users prefer to use names instead of IP addresses, for obvious reasons. So, the process of using names and, most frequently, using a Domain Name System (DNS) to identify the IP address that corresponds to a name is important for end users. Router and switch administrators like to use names in many cases, for the same reason that end users like to use names. When the administrator uses a PC or workstation, that...

Ive Learned a Lot About CCNA Topics Through Experience But I Will Not Be Taking the ICND Course Now What

If you feel that you know a fair amount about CCNA topics already but are worried about the topics you simply just have not worked with, then this strategy is for you. This book is designed to help you figure out what CCNA topics you need some help with and then help you learn about them. Here's the simple strategy for you Strategy 1 Use this book exactly as described in the opening pages of Chapters 2 through 8. Each of the foundational chapters begins with a quiz that helps you assess what...

Whats on the CCNA Exam

Every test-taker would like to know exactly what is on the CCNA exam, as well as the other Cisco certification exams. Well, to be honest, exactly what is on the exam is a very closely guarded secret. Only those who write the questions for Cisco, and who have access to the entire question database, truly know what is really on the exam. Cisco makes fairly general CCNA exam content available to the public at the Web site In fact, two direct quotes from this Web site sumarize the exam CCNA...

How This Book Can Help You Prepare and Pass the CCNA Exam

The first goal for this book came at the request of the Cisco Career Certifications team they asked that we build a book that didn't just help you pass a test, but also for a book that helped you really understand the concepts and implementation details. (Because Cisco Press is the only Cisco authorized publisher, we tend to listen to Cisco ) A second goal was to make the content of the book the most comprehensive coverage of CCNA-related topics available, but without a lot of coverage of...

All About the Cisco Certified Network Associate Certification

Congratulations You have made your first step in beginning your journey to joining the Cisco Career Certifications group of certified professionals. CCNA is the first step into your journey. The Cisco Certified Network Associate (CCNA) certification is the most popular certification among all Cisco certifications. CCNA certification is a prerequisite for several other Cisco Certifications, which of course adds to its popularity. The exam itself is a computer-based exam, with multiple choice,...

ICMP Echo Request and Echo Reply

The ICMP Echo and Echo Reply messages are sent and received by the ping command. In fact, when people say that they sent a ping packet, they really mean that they sent an ICMP Echo Request. These two messages are very much self-explanatory. The Echo Request simply means that the host to which it is addressed should reply to the packet. The Echo Reply is the ICMP message type that should be used in the reply. The Request includes some data, which can be specified by the ping command whatever...

The TCPIP and Net Ware Protocols

Two of the most pervasively deployed protocols are TCP IP and Novell NetWare these also are the two key protocol architectures covered on the CCNA exam. TCP IP and NetWare are covered in much more detail in the upcoming chapters. This short section compares TCP IP, Novell, and OSI. The goal is to provide some insight into what some popularly used terminology really means. In particular, routing is defined as a Layer 3 process this section reviews how that term relates to TCP IP and NetWare. For...

Network Address Translation

Network Address Translation (NAT) is an RFC-defined function implemented in IOS that allows a host that does not have a valid registered IP address to communicate with other hosts through the Internet. The hosts may be using private addresses or addresses assigned to another organization in either case, NAT allows these addresses that are not Internet-ready to continue to be used but still allow communication with hosts across the Internet. NAT achieves its goal by using a valid address in some...

Ipx Rip Sap and GNS

The CCNA exam requires you not only to know the differences between IPX RIP and IP RIP, but to also know two other NetWare protocols used by the router Service Advertisement Protocol (SAP) and Get Nearest Server (GNS). Because IPX RIP and IP RIP were originally based on the same protocol (XNS RIP), the two are very similar. SAP and GNS have no equivalent feature in TCP IP. RIP for IPX works in a similar manner to IP RIP. The most obvious difference is that IPX RIP advertises IPX network...

Filtering IPX Traffic and SAPs

IPX access lists can be used to filter IPX packets sent by clients and servers, just as IP access lists are used to filter IP packets. However, similar functions can be performed by using Service Advertising Protocol (SAP) filters, which filter SAP updates sent by servers and routers. SAP filters are more common because they can be used to prevent clients and servers from trying to send packets, as well as to reduce the overhead of SAP updates. CCNAs deal with SAPs and SAP filtering on a...

Router Components

Before examining the IOS, a review of hardware and hardware terminology is useful. In addition to handling the logic of routing packets, the IOS controls the use of different physical components, which includes memory, processor, and interfaces. This section of the book reviews common hardware details. All Cisco routers have a console port, and most have an auxiliary port. The console port is intended for local administrative access from an ASCII terminal or a computer using a terminal...

Auto Summary and Route Aggregation

The IOS is optimized to perform routing as fast as possible. Most of the Layer 3 routing performance improvement in the brief history of routers has been through improved algorithms many times those improved algorithms later have been implemented in hardware to provide additional latency improvements. Although these improvements have been a great benefit, it is typically true that any algorithm that searches a list will run more quickly if the list is short, compared to searching a similar list...

RIP1 and IGRPNo Subnet Masks

RIP-1 and IGRP do not transmit the subnet mask in the routing updates, as seen in the debug output examples in this section. As a CCNA, Cisco expects you to be able to articulate the implications of the missing mask to the function of the routing protocol. Several subtle actions are taken in light of the lack of mask information in the update Updates sent out an interface in network X, when containing routes about subnets of network X, contain the subnet numbers of the subnets of network X but...

About the Author

Wendell Odom has worked with networking technology for 15 years. He is currently a Cisco Systems Senior Systems Engineer in the Atlanta, Georgia office, assigned to several large Cisco customers. Prior to joining Cisco in 1999, Wendell provided consulting services on large networks as well as training services. He spent his first eight years in networking working for IBM, helping customers evolve their SNA networks into multiprotocol networks. Wendell is CCIE 1624, is a Certified Cisco Systems...

The network Command

Each network command enables RIP or IGRP on a set of interfaces. However, as a CCNA, you must understand the subtleties to what that really means (as explained in the next several paragraphs.) However, what enables really means in this case is not obvious from Cisco IOS documentation. Also, the parameters for the network command are not intuitive to many people new to Cisco IOS configuration commands therefore, routing protocol configuration, including the network command, is a likely topic for...

Data Link Function 1 Arbitration

Arbitration is needed only when there are instants in time during which it is not appropriate to send data across the media. LANs were originally defined as a shared media on which each device must wait until the appropriate time to send data. The specifications for these data link protocols define how to arbitrate the use of the physical medium. Ethernet uses the carrier sense multiple access collision detect (CSMA CD) algorithm for arbitration. The basic algorithm for using an Ethernet when...

Time Exceeded ICMP Message

The CCNA exam requires that you understand how routing protocols avoid creating routing loops. However, if a loop occurs, the Time To Live (TTL) field in the IP header is used to time out looping packets so that the packets do not loop forever. The Time Exceeded ICMP message is used in conjunction with the IP TTL header field. One of the two codes for Time Exceeded will be described here namely, the Time To Live (TTL) code option. An analogy for Time Exceeded may help. In the 1970s, a science...

Using Secondary Addresses

As a CCNA, Cisco expects you to be comfortable and familiar with IP address planning issues. One such issue involves what to do when there are no more unassigned IP addresses in a subnet. One alternative solution is to change the mask used on that subnet, making the existing subnet larger. However, changing the mask could cause an overlap. For example, if 10.1.4.0 24 is running out of addresses and you make a change to mask 255.255.254.0 (9 host bits, 23 network subnet bits), an overlap can...

OSI Layers

The OSI model consists of seven layers, each of which can (and typically does) have several sublayers. Cisco requires that CCNAs demonstrate an understanding of each layer as well as the protocols that correspond to each OSI layer. The names of the OSI model layers and their main functions are simply good things to memorize. And frankly, if you want to pursue your Cisco certifications beyond CCNA, these names and functional areas will come up continually. The upper layers of the OSI model...

Standard IP Access Lists

Standard access lists can match only by examining the source IP address field in the packet's IP header. Any bit positions in the 32-bit source IP address can be compared to the access list statements for example, a subnet number can be checked. However, the matching is flexible and does not consider the subnet mask in use it is just a math problem A wildcard mask defines the subset of the 32 bits in the IP address that must be matched. As a CCNA, you will be required to fully understand the...

D n

Example 5-2 Albuquerque Router Configuration and EXEC Commands enable secret 5 1 skrN z4oq6OHfB6zu1WG4P 6ZY0 interface Serial0 ip address 10.1.128.251 255.255.255.0 interface Serial1 ip address 10.1.130.251 255.255.255.0 Example 5-2 Albuquerque Router Configuration and EXEC Commands (Continued) n interface Ethernet0 ip address 10.1.1.251 255.255.255.0 Should've taken a left turn here This is Albuquerque C line con 0 password cisco login line aux 0 line vty 0 4 password cisco login Codes C -...

Exams Required for Certification

To certify for CCNA, a single exam is required Sylvan Prometric exam number 640-507. For CCDA, a single exam is required as well, but multiple exams are required for CCNP and CCDP. The exams generally match the same topics that are covered in one of the official Cisco courses, but in most cases and certainly on the CCNA exam more topics are covered on the exam than are in the course. Table 1-1 outlines the exams and the courses with which they are most closely matched. Course Most Closely...

Extended IP Access Lists

Extended IP access lists are almost identical to standard IP access lists in their use. The key difference between the two types is the variety of fields in the packet that can be compared for matching by extended access lists. To pass the CCNA exam, you must remember all the items that an extended IP access list can check to make a match. As with standard lists, extended access lists are enabled for packets entering or exiting an interface. The list is searched sequentially the first statement...

Command Line Interface

Cisco uses the acronym CLI to refer to the terminal user command-line interface to the IOS. The term CLI implies that the user is typing commands at a terminal, terminal emulator, or Telnet connection. Although you can pass the CCNA exam without ever having used the CLI, actually using the CLI will greatly enhance your chances. To access the CLI, use one of three methods, as illustrated in Figure 2-3. Figure 2-3 CLI Access Regardless of which access method is used, a CLI user initially is...

Do I Know This Already Quiz

The purpose of the Do I Know This Already quiz is to help you decide what parts of this chapter to use. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now. This 12-question quiz helps you determine how to spend your limited study time. The quiz is sectioned into three smaller four-question quizlets, which correspond to the three major topic headings in the chapter. Figure 2-1 outlines suggestions on how to spend your time in this chapter...

Troubleshooting Routing and Routing Protocols

It is no secret that Cisco would very much like all its certification exams CCNA included to be exams that prove that the test taker can build and troubleshoot live networks. Some people work with Cisco routers daily. Others' current job function does not allow frequent access to routers if this applies to you, you likely are trying to pass this certification so that you can move into jobs that involve routers and switches. The show ip route command has a myriad of options that will be helpful...

Data Encapsulation

The concept of placing data behind headers (and before trailers) for each layer is typically called encapsulation by Cisco documentation. As seen previously in Figure 3-2, when each layer creates its header, it places the data given to it by the next-higher layer behind its own header, thereby encapsulating the higher layer's data. In the case of a data link (Layer 2) protocol, the Layer 3 header and data are placed between the Layer 2 header and the Layer 2 trailer. The physical layer does not...

Navigating the Ios Cli

Several references are available for help when you are using the IOS. IOS documentation is available on CD and is free from Cisco if you own one router or switch under a current maintenance agreement. Paper documentation is also available from Cisco. If you prefer, Cisco Press offers the Cisco Documentation series (more information at www.ciscopress.com). In addition, all Cisco documentation is available online at Cisco's Web site (www.cisco.com univercd home home.htm) the IOS command reference...

Binary View of Subnetting

The benefit of a binary definition of subnetting is that it is exact. For a full understanding of subnetting particularly more advanced subnetting topics as well as other IP addressing and routing topics beyond the scope of this book, an exact definition is required. If your job will include planning subnet number assignment or troubleshooting, this binary understanding will be useful. Ray 150.150.1.0 150.15a2.0 Vinnie Ray 150.150.1.0 150.15a2.0 Vinnie A review of some basic concepts relating...

LAN Switching

An Ethernet switch appears to use the same logic as a transparent bridge. However, the internal logic of the switch is optimized for performing the basic function of choosing when to forward and when to filter a frame. Just as with a transparent bridge, the basic logic of a LAN switch is as follows Step 2 If the destination is a broadcast or multicast, forward on all ports. Step 3 If the destination is a unicast and the address is not in the address table, forward on all ports. Step 4 If the...

Cisco CCNA Exam 640507 Certification Guide

Cisco CCNA Exam 640-507 Certification Guide Copyright 2000 Lacidar Unlimited, Inc. Cisco Press logo is a trademark of Cisco Systems, Inc. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the publisher, except for the inclusion of brief quotations in a review. Printed in the United States of America...

Choosing Which IOS Image to Load

The CCNA exam requires you to be proficient in configuring a router to load an IOS image from many sources. Two methods are used by a router to determine where it tries to obtain an IOS image to execute. The first is based on the value of the configuration register, which is a 16-bit software register in Cisco's more recently developed routers. (Some older routers had a hardware configuration register, with jumpers on the processor card, to set bits to a value of 0 or 1.) The second method used...

Connection Oriented Versus Connectionless Protocols

The terms connection-oriented and connectionless have some relatively well-known connotations inside the world of networking protocols. However, the typical connotation can be a bit misleading. For instance, most people correlate connection-oriented protocols with reliable or error-recovering protocols because the two features are often implemented by a single protocol. However, connection-oriented protocols do not have to provide error recovery, and error-recovering protocols do not have to be...

Qa

As mentioned in Chapter 1, All About the Cisco Certified Network Associate Certification, the questions and scenarios in this book are more difficult than what you should experience on the actual exam. The questions do not attempt to cover more breadth or depth than the exam however, they are designed to make sure that you know the answer. Rather than allowing you to derive the answer from clues hidden inside the question itself, the questions challenge your understanding and recall of the...

LAN Switch Configuration

Cisco expects CCNAs to master the concepts behind LAN switching and VLANs. This mastery includes the ability to configure IOS-based LAN switches using the IOS CLI. This section outlines the similarities of the switch IOS CLI to the router IOS CLI, as well as contrasting the commands, syntax, and required configuration elements unique to switches. Not all Cisco LAN switches provide an IOS CLI interface to the network engineer. Cisco wants its certifications to prove that the candidate knows the...

Recommended Training Path for CCNA

Cisco recommends that you take two courses before you take the CCNA exam. The first, Internetworking Technology Multimedia (ITM), is a CD-based course that you can order directly from Cisco currently for 50. This course covers many of the protocol basics needed for CCNA. The other suggested course is the instructor-led Interconnecting Cisco Network Devices (ICND) course, which is available from almost every Cisco training partner (for a list of training partners, go to The ICND course replaces...