Do I Know This Already Quiz

The purpose of the Do I Know This Already quiz is to help you decide if you really need to read this entire chapter. If you already intend to read the entire chapter, you do not need to answer these questions now. The 10-question quiz, derived from the major sections in the Foundation Topics portion of the chapter, helps you determine how to spend your limited study time. Table 3-1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions that correspond...

Commands and Applications Used to Isolate Problems Occurring at the Transport Layer

To ascertain that a problem is rooted at the transport layer rather than at a layer below it, you must use proper tools and commands. You can test the operability of Layers 1, 2, and 3 by using the Windows commands ping, tracert, netstat, and nbtstat. If the results prove that the lower layers (physical, data link, and network) are in good working order, you can focus your attention on Layer 4-related issues such as filters, policies, quality of service (QoS) tools, and so on. You can use the...

About the Technical Reviewers

Craig Dorry, CCIE No. 9072, is a network architect and Tier 3 network support engineer for AT& T Solutions, where he is the escalation contact for high-profile and business-impacting network issues. Craig has more than eight years of experience in network implementation and support at the LAN and WAN level. He has strong knowledge of routing protocol performance issues as well as network diagnostic and management equipment. Don Johnston is a certified Cisco Systems instructor and consultant...

Cisco Press

800 East 96th Street, 3rd Floor Indianapolis, Indiana 46240 USA CCNP CIT Exam Certification Guide Second Edition Amir S. Ranjbar, MSc., CCIE No. 8669 Copyright 2004 Cisco Systems, Inc. 800 East 96th Street, 3rd Floor Indianapolis, IN 46240 USA 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...

Resolving Problems at the Physical or Data Link Layer

Chapter 7, Isolating a Problem at the Physical or Data Link Layer, lists several common symptoms of problems occurring at the physical or data link layer. Table 13-1 provides a summary of those symptoms for your review. Table 13-1 Common Symptoms of Physical and Data Link Layer Problems Table 13-1 Common Symptoms of Physical and Data Link Layer Problems Common Symptoms of Problems Occurring at the Physical Layer Common Symptoms of Problems Occurring at the Data Link Layer No component above the...

Gathering Network Symptoms

Figure 5-1 displays the process of gathering symptoms from a network using a flowchart. Figure 5-1 sends the message that you must first ascertain that the problem is within your area of responsibility. Next, you must determine whether the symptoms and facts gathered are enough to identify the cause and take corrective actions. Sometimes gathering more facts is necessary when you have gathered enough information and determined the cause, you can take corrective actions. The stages of gathering...

Gathering End System Symptoms

This section presents a process you can use to gather symptoms from end systems. Figure 5-2 displays this process with a flowchart. The process starts with interviewing the user and then calls for analyzing, determining, and documenting the symptoms. Finally, you correct the problem if it is possible. NOTE This book focuses on troubleshooting network connectivity. You might need to seek help from external vendors or workstation and server administrators to effectively troubleshoot problems at...

Analyzing Commands and Applications Used to Isolate Problems Occurring at the Physical and Data Link Layers

This section covers commands that you use to isolate problems at the physical and data link layers. This section also demonstrates isolating problems at physical and data link layers through some examples. Table 7-2 shows end system commands used to isolate problems at the physical and data link layers. The first part of this table lists general commands. The second section lists commands you enter at an end system running a version of the Windows operating system. In the third part of Table...

Correcting Problems Occurring at the Transport and Application Layers

This section details a brief yet beneficial procedure to be followed when correcting problems occurring at the transport and application layers (or in general). Because the order of execution is important, the steps are presented as a numbered list 1. Be sure that you have a saved configuration for the device whose configuration you are about to change. During the course of troubleshooting, you should always be able to revert back to a known initial state. Casually speaking, you want to make...

Identifying Commands and Applications Used to Correct Problems Occurring at the Application Layer

Service Timestamps Cisco

This section presents some commands that you can use to correct problems occurring at the application layer. The selected commands relate to SNMP, NTP, and Dynamic Host Configuration Protocol (DHCP). Of course, you can use other commands to configure and correct application layer problems. The Cisco Internetwork Troubleshooting (CIT) course intends to familiarize you with the troubleshooting process, rather than listing and explaining all Cisco IOS commands. This book also discusses those same...

The Encapsulated Data Flow Process

Lighting Truss Guy Wire

This section discusses the stages of data flow through a network that interconnects remote end systems and segments using Cisco routers and switches. This discussion includes the topic of encapsulation and decapsulation (or de-encapsulation), along with the different forwarding filtering performed by routers and switches. Figure 3-1 shows end system Host A and end system Host B communicating on a network. The encapsulated data flow process has four stages. In Figure 3-1, Stages 1 through 4...

Commands and Applications Used to Correct Problems Occurring at the Physical and Data Link Layers

The CIT course discusses certain commands with regards to correcting physical and data link problems. This section discusses those commands. Neither the CIT course nor this book imply by any means that you can fix all physical and data link layer problems by using these commands. The commands are listed and briefly described in Table 8-2. From there, a more detailed discussion of these controller and interface configuration commands is provided. The last part of this section gives examples on...

Foundation Summary

The Foundation Summary section of each chapter lists the most important facts from that chapter. Although this section does not list every fact from the chapter that will be on your CCNP exam, a well-prepared CCNP candidate should at a minimum know all the details in each Foundation Summary before taking the exam. Following are some common symptoms of network layer problems No component on the failing link appears to be functional above the network layer. The network is functional but is...

Analyzing Cisco Command and Application Output to Isolate Problems Occurring at the Network Layer

This section describes several important Cisco IOS commands that display information that is useful for isolating network layer problems (see Table 9-3). Following that, a scenario-style example demonstrates how you can use the commands listed in Table 9-3 to help isolate a realistic network layer problem. The first few commands listed in Table 9-3 are marked as general commands because they might reveal issues related to many aspects of configuration at the network layer (addressing, routing,...