Tài liệu Cisco Internetwork Troubleshooting pptx

CIT
Cisco Internetwork
Troubleshooting
Version 5.2
Student Guide
Text Part Number: ILSG Production Services: 03.25.05
Copyright 2005, Cisco Systems, Inc. All rights reserved.
Cisco Systems has more than 200 offices in the following countries and regions. Addresses, phone numbers, and fax
numbers are listed on the Cisco Website at www.cisco.com/go/offices.
Argentina Australia Austria Belgium Brazil Bulgaria Canada Chile China PRC Colombia Costa Rica
Croatia Cyprus Czech Republic Denmark Dubai, UAE Finland France Germany Greece
Hong Kong SAR Hungary India Indonesia Ireland Israel Italy Japan Korea Luxembourg Malaysia
Mexico The Netherlands New Zealand Norway Peru Philippines Poland Portugal Puerto Rico Romania
Russia Saudi Arabia Scotland Singapore Slovakia Slovenia South Africa Spain Sweden Switzerland
Taiwan Thailand Turkey Ukraine United Kingdom United States Venezuela Vietnam Zimbabwe
Copyright 2005 Cisco Systems, Inc. All rights reserved. CCSP, the Cisco Square Bridge logo, Follow
Me Browsing, and StackWise are trademarks of Cisco Systems, Inc.; Changing the Way We Work, Live,
Play, and Learn, and iQuick Study are service marks of Cisco Systems, Inc.; and Access Registrar, Aironet, ASIST,
BPX, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, Cisco, the Cisco Certified Internetwork Expert logo,
Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Empowering
the Internet Generation, Enterprise/Solver, EtherChannel, EtherFast, EtherSwitch, Fast Step, FormShare, GigaDrive,
GigaStack, HomeLink, Internet Quotient, IOS, IP/TV, iQ Expertise, the iQ logo, iQ Net Readiness Scorecard,
LightStream, Linksys, MeetingPlace, MGX, the Networkers logo, Networking Academy, Network Registrar,
Packet, PIX, Post-Routing, Pre-Routing, ProConnect, RateMUX, ScriptShare, SlideCast, SMARTnet, StrataView
Plus, SwitchProbe, TeleRouter, The Fastest Way to Increase Your Internet Quotient, TransPath, and VCO are
registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or Website are the property of their respective owners. The use of
the word partner does not imply a partnership relationship between Cisco and any other company. (0501R)
DISCLAIMER WARRANTY: THIS CONTENT IS BEING PROVIDED !AS IS." CISCO MAKES AND YOU RECEIVE NO
WARRANTIES IN CONNECTION WITH THE CONTENT PROVIDED HEREUNDER, EXPRESS, IMPLIED, STATUTORY
OR IN ANY OTHER PROVISION OF THIS CONTENT OR COMMUNICATION BETWEEN CISCO AND YOU. CISCO

SPECIFICALLY DISCLAIMS ALL IMPLIED WARRANTIES, INCLUDING WARRANTIES OF MERCHANTABILITY,
NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING,
USAGE OR TRADE PRACTICE. This learning product may contain early release content, and while Cisco believes it to be
accurate, it falls subject to the disclaimer above.
Table of Contents
Course Introduction 1
Overview 1
Learner Skills and Knowledge 1
Course Goals and Objectives 2
Course Flow 3
Additional References 4
Cisco Glossary of Terms 4
Your Training Curriculum 5
Establishing a Baseline 1-1
Overview 1-1
Module Objectives 1-1
Creating Network Configuration Documentation 1-3
Overview 1-3
Objectives 1-3
Identifying the Components of a Network Configuration Table 1-4
Example: Network Configuration Table (Router) 1-6
Example: Network Configuration Table (Switch) 1-7
What Are the Components of a Topology Diagram? 1-8
Example: Network Topology Diagram No. 1 1-10
Example: Network Topology Diagram No. 2 1-11
Discovering Network Configuration Information 1-12
Example: Discovering Network Configuration of a Router 1-12
Example: Discovering Network Configuration of a Standard Switch 1-14
Creating Network Documentation 1-16
Identifying the Guidelines for Creating Network Documentation 1-18

Example: Creating Successful Network Documentation 1-19
Summary 1-20
Creating End-System Network Configuration Documentation 1-21
Overview 1-21
Objectives 1-21
What Are the Components of an End-System Network Configuration Table? 1-22
Example: End-System Network Configuration Table 1-24
What Are the Components of an End-System Network Topology Diagram? 1-25
Example: Topology Diagram with Both Network Devices and End Systems 1-27
What Are the Commands and Applications Used to Gather Information About
End-System Network Configurations? 1-28
What Is the Process of Discovering End-System Network Configuration Information? 1-32
Example: Discovering End-System Network Configurations 1-32
Identifying the Guidelines for Creating End-System Network Configuration Documentation 1-34
Example: Creating Successful End-System Network Configuration Documentation 1-35
Summary 1-36
Module Summary 1-37
References 1-37
Module Self-Check 1-38
Module Self-Check Answer Key 1-40
Determining an Effective Troubleshooting Strategy 2-1
Overview 2-1
Module Objectives 2-1
Applying a Layered Model to a Network 2-3
Overview 2-3
Objectives 2-3
What Are the Differences Between Layered Networking Models? 2-4
Example: Comparing the OSI Model with the TCP/IP Model 2-4
Identifying the Encapsulated Data Flow Process 2-6
ii Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.

Where Do Network Devices Map in a Logical Model? 2-7
Summary 2-8
Describing the General Troubleshooting Process 2-9
Overview 2-9
Objectives 2-9
What Are the Stages of the General Troubleshooting Process? 2-10
What Is the Gathering Symptoms Stage? 2-11
What Is the Isolate the Problem Stage? 2-12
What Is the Correct the Problem Stage? 2-13
Summary 2-14
Gathering Symptoms 2-15
Overview 2-15
Objectives 2-15
Gathering Network Symptoms 2-16
Gathering User Symptoms 2-19
Example: Gathering Network Symptoms from the End User 2-20
Gathering End-System Symptoms 2-21
Summary 2-24
Selecting a Troubleshooting Approach 2-25
Overview 2-25
Objectives 2-25
What Is the Bottom-Up Troubleshooting Approach? 2-26
What Is the Top-Down Troubleshooting Approach? 2-27
What Is the Divide-and-Conquer Troubleshooting Approach? 2-28
Selecting a Troubleshooting Approach 2-29
Example: Selecting a Troubleshooting Approach 2-30
Summary 2-31
Module Summary 2-32
References 2-32
Module Self-Check 2-33

Module Self-Check Answer Key 2-38
Resolving Problems at the Physical and Data Link Layers 3-1
Overview 3-1
Module Objectives 3-1
Isolating the Problem at the Physical and Data Link Layers 3-3
Overview 3-3
Objectives 3-3
What Are the Symptoms of Problems at the Physical Layer? 3-4
What Are the Symptoms of Problems at the Data Link Layer? 3-6
Analyzing Commands and Applications at the Physical and Data Link Layers 3-8
Example: Isolating Serial Interface Problems at the Physical Layer 3-13
Example: Isolating Frame Relay Problems at the Data Link Layer 3-17
Example: Isolating Ethernet Problems at the Physical and Data Link Layers 3-24
Example: Isolating Fast Ethernet Problems at the Physical and Data Link Layers 3-27
Example: Isolating a Problem at the Physical and Data Link Layers 3-29
Isolating Problems at the Physical and Data Link Layers 3-35
Example: Isolating Problems at the Physical and Data Link Layers 3-36
Summary 3-37
Correcting the Problem at the Physical and Data Link Layers 3-39
Overview 3-39
Objectives 3-39
What Are the Commands and Applications to Correct Problems at the Physical and Data Link
Layers? 3-40
Example: Correcting a Serial Interface Problem at the Physical Layer 3-41
Example: Correcting a Frame Relay Problem at the Data Link Layer 3-44
Example: Correcting an Ethernet Problem at the Physical and Data Link Layers 3-48
Copyright 2005, Cisco Systems, Inc. Cisco Internetwork Troubleshooting (CIT) v5.2 iii
Example: Correcting Fast Ethernet Problems at the Physical and Data Link Layers 3-51
Example: Correcting a Problem at the Physical and Data Link Layers 3-54
What Are Physical and Data Link Layer Support Resources? 3-58

Correcting Problems Occurring at the Physical and Data Link Layers 3-60
Summary 3-62
Module Summary 3-63
References 3-63
Module Self-Check 3-64
Module Self-Check Answer Key 3-66
Resolving Problems at the Network Layer 4-1
Overview 4-1
Module Objectives 4-1
Isolating the Problem at the Network Layer 4-3
Overview 4-3
Objectives 4-3
What Are the Symptoms of Problems at the Network Layer 4-4
Analyzing Cisco Command and Application Output at the Network Layer 4-6
Identifying End-System Commands and Applications at the Network Layer 4-15
Example: Isolating an Access List Problem at the Network Layer 4-17
Example: Isolating an IP Addressing Problem at the Network Layer 4-27
Example: Isolating Problems at the Network Layer 4-33
Isolating Problems at the Network Layer 4-39
Example: Isolating Problems Occurring at the Network Layer 4-40
Summary 4-41
Correcting the Problem at the Network Layer 4-43
Overview 4-43
Objectives 4-43
What Are the Cisco Commands Used at the Network Layer? 4-44
What Are the End-System Commands and Applications Used at the Network Layer? 4-50
Example: Correcting an Access List Problem at the Network Layer 4-51
Example: Correcting an IP Addressing Problem at the Network Layer 4-57
Example: Correcting Problems at the Network Layer 4-62
What Are the Network Layer Support Resources? 4-67

Correcting Problems at the Network Layer 4-68
Summary 4-70
Module Summary 4-71
References 4-71
Module Self-Check 4-72
Module Self-Check Answer Key 4-74
Resolving Problems at the Transport and Application Layers 5-1
Overview 5-1
Module Objectives 5-1
Isolating the Problem at the Transport and Application Layers 5-3
Overview 5-3
Objectives 5-3
What Are the Symptoms of Problems at the Transport Layer? 5-4
What Are the Symptoms of Problems at the Application Layer? 5-6
Analyzing Command and Application Output at the Transport Layer 5-8
Example: Isolating an Extended Access List Problem at the Transport Layer 5-12
Example: Isolating a Problem at the Transport Layer 5-21
Analyzing Command and Application Output at the Application Layer 5-31
Example: Isolating a TFTP Problem at the Application Layer 5-38
Example: Isolating a Problem at the Application Layer 5-44
Isolating Problems at the Transport and Application Layers 5-53
Example: Isolating a Problem Occurring at the Transport or Application Layer 5-54
Summary 5-55
iv Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Correcting the Problem at the Transport and Application Layers 5-57
Overview 5-57
Objectives 5-57
What Are the Commands and Applications Used at the Transport Layer 5-58
Example: Correcting an Extended Access List Problem at the Transport Layer 5-59
Example: Correcting a Problem at the Transport Layer 5-61

What are the Commands and Applications Used at the Application Layer? 5-70
Example: Correcting a TFTP Problem at the Application Layer 5-73
Example: Correcting a Problem at the Application Layer 5-76
What Are Transport and Application Layer Support Resources? 5-81
Correcting Problems at the Transport and Application Layers 5-83
Summary 5-85
Module Summary 5-86
References 5-86
Module Self-Check 5-87
Module Self-Check Answer Key 5-89
CIT
Course Introduction
Overview
Cisco Internetwork Troubleshooting (CIT) v5.2 is designed to provide learners with hands-on
experience in troubleshooting suboptimal performance in a converged network and is an
integral part of any approach to obtain the technical proficiency of Cisco CCNP
®
. The course
deepens the technical ability of the learner rather than introducing new baseline technology.
Learner Skills and Knowledge
This subtopic lists the skills and knowledge that learners must possess to benefit fully from the
course. The subtopic also includes recommended Cisco learning offerings that learners should
complete in order to benefit fully from this course.
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 3
Learner Skills and Knowledge
Interconnecting Cisco Network Devices
(ICND)
Building Cisco Multilayer Switched
Networks (BCMSN)
Building Cisco Remote Access Networks

(BCRAN)
Building Scalable Cisco Internetworks
(BSCI)
2 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Course Goals and Objectives
This topic describes the course goal and objectives.
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 4
!To provide learners with hands-on
experience in troubleshooting sub-
optimal performance in a converged
network"
Cisco Internetwork Troubleshooting (CIT) v5.2
Course Goal
Upon completing this course, you will be able to meet these objectives:
Establish a baseline so that the network topology and configuration are diagrammed and
tabulated
Determine an effective troubleshooting strategy so that learners can detect, isolate, and
correct network problems consistently
Isolate and correct problems at the physical and data link layers so that framed data moves
from one end of a data link to another at the expected data error rate determined in the
network baseline
Isolate and correct problems at the network layer so that connectivity at the network layer
can be verified, the routing tables show reachability to all expected network devices
specified in the baseline, and traffic is flowing over the correct path detailed in the network
baseline
Isolate and correct problems at the transport and application layers so that applications
transmit data at an expected throughput, latency, and jitter based on the network baseline
Copyright © 2005, Cisco Systems, Inc. Course Introduction 3
Course Flow
This topic presents the suggested flow of the course materials.

©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 5
Course Flow
Creating Network
Configuration
Documentation
Course
Introduction
Creating End-System
Network Configuration
Documentation
Correcting the
Problem
(Transport &
Application)
Lunch
Describing a General
Troubleshooting
Process
Isolating the Problem
(Network Layer)
Isolating the Problem
(Transport &
Application)
A
M
P
M
Day 1Day 2Day 3Day 4Day 5
Applying a
Layered Model

to a Network
Gathering
Symptoms
Selecting a Trouble-
shooting Approach
Isolating the Problem
(Physical & Data Link)
Correcting the
Problem
(Network Layer)
Correcting the
Problem (Cont.)
(Transport &
Application)
Correcting the
Problem (Cont.)
(Physical & Data Link)
Correcting the
Problem
(Physical & Data Link)
Correcting the
Problem (Cont.)
(Network Layer)
Correcting the
Problem (Cont.)
(Network Layer)
Wrap-Up
The schedule reflects the recommended structure for this course. This structure allows enough
time for the instructor to present the course information and for you to work through the lab
activities. The exact timing of the subject materials and labs depends on the pace of your

specific class.
4 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Additional References
This topic presents the Cisco icons and symbols used in this course, as well as information on
where to find additional technical references.
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 6
PC
Cisco Icons and Symbols
Router
Workgroup
Switch
Network
Cloud, Gray
File
Server
Laptop
Line: Serial
Line: Ethernet
Terminal
Hub
Network
Cloud, White
Token Ring
Token
Ring
Cisco Glossary of Terms
For additional information on Cisco terminology, refer to the Cisco Internetworking Terms and
Acronyms glossary of terms at />Copyright © 2005, Cisco Systems, Inc. Course Introduction 5
Your Training Curriculum
This topic presents the training curriculum for this course.

©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 7
Expand Your Professional Options
and Advance Your Career
Cisco Internetwork Troubleshooting (CIT)
Professional
CCIE
CCNP
CCNP
CCNA
CCNA
Associate
Professional-level recognition in CIT
/>Recommended Training Through
Cisco Learning Partners
Required
Exam
CIT
642-831
640-821
640-811
Cisco Internetwork
Troubleshooting (CIT)
Interconnecting Cisco Network
Devices (ICND)
Introduction to Cisco Networking
Technologies (INTRO)
CCNA Exam (CCNA); can take this
exam OR both 640-821 & 640-811)
640-801
Expert

Cisco Career Certifications
Cisco Qualified Specialist focused certifications demonstrate significant competency in specific
technology areas, solutions, or job roles. Individuals who have earned an associate-level career
certification or higher are eligible to become qualified in these focused areas. With one or more
specialist certifications, network professionals can better align their core expertise with current
industry needs.
For more information on the Cisco Qualified Specialist focused certification, visit
/>unity_tool_launch.html.
6 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Module 1
Establishing a Baseline
Overview
Some of the biggest challenges facing the information technology (IT) world are the expenses
that are incurred as a result of network outages. The negative impact of these expenses should
make it a high priority of network professionals to be able to diagnose and correct a network
problem as efficiently as possible. To help accomplish this, a baseline should be established to
provide a snapshot of the configuration of a network while it is performing at an acceptable
level. Using baseline information as a standard reduces the time that troubleshooters need to
spend learning about the structure and configuration of a network and helps them know when
they have reached the goal of returning the network to its baseline operation. Without a
baseline, troubleshooters are left with having to make guesses and estimates about whether they
have reached their goal, and their efforts will most likely occur in a haphazard and inefficient
manner.
Module Objectives
Upon completing this module, you will be able to establish a baseline so that the topology and
configuration is diagrammed and tabulated. This ability includes being able to meet these
objectives:
Create network configuration documentation
Create an end-system configuration table and end-to-end topology diagram
1-2 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.

Lesson 1
Creating Network
Configuration Documentation
Overview
When troubleshooting a network, a troubleshooter uses a baseline to efficiently diagnose and
correct network problems. The baseline information for a network is captured on
documentation such as network configuration tables and topology diagrams. This lesson
discusses the creation of relevant and accurate network documentation as a troubleshooting tool
for returning a suboptimal or failing network back to an acceptable condition. The information
contained in this lesson assumes a worst-case scenario in which you are almost completely
unfamiliar with a network and need to create documentation from scratch.
Useful network documentation will make you a more effective troubleshooter by saving you
time and effort. When the configuration of your network is failing or performing suboptimally,
a network configuration table will provide you with a saved configuration that should perform
at an acceptable level. Network documentation will also prevent you from performing the time-
consuming and error-prone process of creating a network configuration from scratch.
Objectives
Upon completing this lesson, you will be able to create network configuration documentation.
This ability includes being able to meet these objectives:
Identify the components of a network configuration table
Identify the components of a topology diagram
Discover network configuration information
Describe the process for creating network documentation
Describe the guidelines for creating network documentation
1-4 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Identifying the Components of a Network
Configuration Table
This topic identifies the components of a network configuration table.
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-2
Network Configuration Tables

When creating a network configuration table for
troubleshooting, you should document the following:
The device name
Data link layer addresses and implemented features
Network layer addresses and implemented features
A network configuration table shows accurate records of the hardware and software used in a
network. The components of a network configuration table are the different types of data that
will comprehensively document the hardware and software components of a network.
When creating a network configuration table for troubleshooting, you should document the
following:
The device name
Data link layer addresses and implemented features
Network layer addresses and implemented features
Any important information about the physical aspects of the device
Note The decision of what specific components to include on network documentation should be
made by someone who has knowledge of the network being documented and has some
previous experience troubleshooting that network.
Copyright © 2005, Cisco Systems, Inc. Establishing a Baseline 1-5
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-3
Network Configuration Table Components
Related to Troubleshooting
Physical Layer
CPU Type
Flash Memory
DRAM
Media Types
Speed
Duplex
WAN Circuits
Interface Names

Data Link Layer
Device Name
Device Model
MAC Address
Duplex
Port Identifier
STP State
STP Route Bridge
PortFast
EtherChannel
Spanning Tree
VLANs
Port Security
Encapsulation
Trunk Status
Network Layer
IP Address
Secondary IP Address
Subnet Mask
IP Routing Protocol(s)
Access Lists
IP Addresses of
Neighboring Devices
Tunnels
Loopbacks
Because of the complex nature of most networks, there is a great deal of information that you
could possibly record. To simplify things, troubleshooters can separate the components of a
network configuration table related to troubleshooting into categories based on their
relationship to the layers of the commonly referenced TCP/IP networking model.
Network documentation can vary, depending on the purpose of the documentation and the

types of devices that are being documented. A comprehensive configuration table constructed
for the purpose of troubleshooting will contain different components than one that is
constructed for budgetary tracking or maintenance purposes. Some data components, such as
speed, are not useful for a device, such as a router; however, these components are crucial
pieces of information to record for a switch. A multilayered switch would require components
pertaining to both routers and switches.Because similar types of information are contained
within each device, it would be possible to combine network configuration tables for routers
and switches; however, it usually makes sense to use separate tables.
Components will also vary depending on the features implemented on the devices. The Router
ID (RID) number would be an important piece of information to record about a router running
Open Shortest Path First (OSPF). However, if you were running only Enhanced Interior
Gateway Routing Protocol (EIGRP), you would not document the RID number.
1-6 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Example: Network Configuration Table (Router)
In this example, the following categories are used to document the properties of the devices:
Device name, model
Interface name
MAC address
IP address and subnet mask
IP routing protocol(s)
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-4
Device Name,
Model
Interface
Name
MAC
Address
IP Address and
Subnet Mask
IP Routing

Protocol(s)
Etna,
Cisco1760-V
Vesuvius,
Cisco2611XM
fa0/0
fa0/1
s0/1
s1/1
s0/1
s1/0
0007.8580.a159
0007.8550.a160




10.2.3.1/16
10.0.1.1/16
192.168.34.1/24
172.18.1.1/16
192.168.34.2/24
172.18.2.1/16
EIGRP 10
EIGRP 10
OSPF
EIGRP 10
OSPF
EIGRP 10
An Example of a Network Configuration

Table (Router)
A network configuration table can sometimes contain information that can be used to describe a
router.
Copyright © 2005, Cisco Systems, Inc. Establishing a Baseline 1-7
Example: Network Configuration Table (Switch)
In this example, the following categories have been used to document the properties of the
switch:
Device name and model
Management IP address
Port name
Speed
Duplex
STP state
PortFast
Trunk status
EtherChannel
VLANs
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-5
An Example of a Network Configuration
Table (Switch)
Catalyst Name,
Model, Management
IP Address
Port
NameSpeed
STP State
(Fwd or Block)
Trunk
StatusDuplex
PortFast

(Yes or No)
Ether-
Channel
(L2 or L3)
VLANs
Burlington, WS-
C3550-24-SMI,
10.3.2.33/27
fa0/1
fa0/2
fa0/3
fa0/4
fa0/5
fa0/6
fa0/7
10
100
100
A-100
A-100
A-100
A-100
Full
Full
Half
A-Full
A-Full
A-Full
A-Full
Fwd

Block
Fwd
Fwd
Fwd
Fwd
Fwd
No
No
Yes
No
No
No
No
On
Off
Off
On
On
On
On
-
-
-
L2
L2
L2
L2
-
-
4

1
2
3
5
Occasionally a network configuration table can be used to document the characteristics of a
standard switch.
1-8 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
What Are the Components of a Topology
Diagram?
This topic identifies the components of a network topology diagram.
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-8
The Components of a Network Topology
Diagram
A topology diagram is a graphical representation of a network. The topology diagram illustrates
how each device in a network is connected, while also detailing the aspects of its logical
architecture. Topology diagrams share many of the same components as their network
configuration table counterparts.
Each network device should be represented on the diagram with consistent notation or a
graphical symbol, and each logical and physical connection should be represented using a
simple line or some other appropriate symbol. At a minimum, most topology diagrams include
illustrations of all devices and how those devices are connected.
Many topologies also include network cloud symbols. A labeled cloud symbol is often
employed to represent entities that are either outside of the autonomous control of your network
or outside the scope of the topology diagram. Put simply, labeled cloud symbols are
placeholders signifying that a network, or collection of networks, exists; however, knowing
anything about those networks other than their existence is not particularly relevant to the
diagram.
Copyright © 2005, Cisco Systems, Inc. Establishing a Baseline 1-9
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-9
Topology Diagram Components

Physical Layer
Device Name
Media Type
Interface Name
Speed
Data Link Layer
MAC Address
VLANs
EtherChannel
Trunk
STP Route
Encapsulation
Network Layer
IP Address
Subnet Mask
Routing Protocol(s)
Although the components of a topology diagram can be restricted to a particular layer of the
TCP/IP model, most often they are a combination of the most important components of several
logical layers. To illustrate the important components of a network at the Internet TCP/IP layer,
you might include IP addresses, subnet masks, and routing protocols.
Some topologies are informal hand-drawn sketches, while others are more elaborate, using
detailed symbols, multiple colors, and different ways to view them. The latter are typically
created using graphics applications that vary in functionality. While some applications can be
used as a solution to manually create a network diagram, others can automatically create and
maintain a topology of an existing network.
1-10 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Example: Network Topology Diagram No. 1
The figure illustrates a topology diagram that includes the following components:
Device name
Interface or port name

IP address
Routing protocol(s)
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-10
Network Topology Diagram
(Example No. 1)
A topology diagram can have many components.
Copyright © 2005, Cisco Systems, Inc. Establishing a Baseline 1-11
Example: Network Topology Diagram No. 2
This example shows the following components of a network topology diagram:
Device name
Interface or port name
IP address
VLANs
Trunks
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-11
Network Topology Diagram
(Example No. 2)
Each topology diagram can have different components.
1-12 Cisco Internetwork Troubleshooting (CIT) v5.2 Copyright © 2005, Cisco Systems, Inc.
Discovering Network Configuration Information
This topic describes the procedure for discovering network configuration information.
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-12
Choose a starting point and view the name and model
of the device. Also view the version of the operating
system that the device is running.
Determine active interfaces and their addresses.
View a summary of the interfaces on the device, including
the IP address/subnet mask, interface name, media type,
and physical and data link operational status.
View the MAC address for any interfaces or ports.

Discovering Network Configurations on
Routers and Multilayer Switches
There is a set procedure for discovering the network configuration of a router.
Example: Discovering Network Configuration of a Router
The following steps outline the procedure for discovering the network configuration of a router
or multilayer switch:
Step 1 Choose a starting point and view the name and model of the device. Also view the
version of the operating system that the device is running.
Enter show version.
Step 2 Determine active interfaces and their addresses.
Enter show ip interfaces.
Step 3 View a summary of the interfaces on the device, including the IP address or subnet
mask, interface name, media type, and physical and data link operational status.
Enter show ip interfaces brief.
Step 4 View the MAC address for any interfaces or ports.
Enter show interface {interface-name} for each interface or enter show
interfaces to see a list of all interfaces at once.
Copyright © 2005, Cisco Systems, Inc. Establishing a Baseline 1-13
©2005 Cisco Systems, Inc. All rights reserved. CIT v5.2 1-13
View details about the spanning-tree status on the device.
View a list of Cisco devices that are directly connected
to the device that you are requesting from.
View details about any connected device, such as its
IP address and capabilities.
View a summary of the IP routing protocols enabled
for the device.
Discovering Network Configurations on
Routers and Multilayer Switches (Cont.)
Step 5 View a summary of the IP routing protocols enabled for the device.
Enter show ip protocols.

Step 6 View details about the spanning-tree status on the device.
Enter show spanning-tree summary
or show spanning-tree vlan {vlan-number}.
Step 7 View a list of Cisco devices that are directly connected to the device that you are
requesting from.
Enter show cdp neighbors [detail] or, if cdp is disabled, enter ping.
Step 8 View details about any connected device, such as its IP address and capabilities.
Enter show cdp entry {device id}, show ip eigrp neighbors, or show ip ospf
neighbor.
Note If CDP is disabled, you may want to enable CDP temporarily to make it easier to discover
information about neighboring devices. However, enabling CDP on your devices does not
guarantee that the neighboring devices will have CDP enabled.