larger cover

Add To My Wish List

Register your product to gain access to bonus material or receive a coupon.

TcL Scripting for Cisco IOS

eBook (Watermarked)

  • Your Price: $37.39
  • List Price: $46.74
  • Includes EPUB and PDF
  • About eBook Formats
  • This eBook includes the following formats, accessible from your Account page after purchase:

    ePub EPUB The open industry format known for its reflowable content and usability on supported mobile devices.

    Adobe Reader PDF The popular standard, used most often with the free Acrobat® Reader® software.

    This eBook requires no passwords or activation to read. We customize your eBook by discreetly watermarking it with your name, making it uniquely yours.

  • Description
  • Sample Content
  • Updates
  • Copyright 2010
  • Dimensions: 7-3/8" x 9-1/8"
  • Pages: 320
  • Edition: 1st
  • eBook (Watermarked)
  • ISBN-10: 0-13-343373-0
  • ISBN-13: 978-0-13-343373-9

A guide to building and modifying Tcl scripts to automate network administration tasks

Streamline Cisco network administration and save time with Tcl scripting

Cisco networking professionals are under relentless pressure to accomplish more, faster, and with fewer resources. The best way to meet this challenge is to automate mundane or repetitive tasks wherever possible. In this book, three Cisco experts show you how to use Tcl scripting for Cisco IOS devices to do just that.

You’ll learn easy techniques for creating, using, and modifying Tcl scripts that run directly on Cisco network devices from the Cisco IOS command line. The authors first teach basic Tcl commands and concepts for capturing and manipulating data and for querying or controlling Cisco equipment. Building on these core skills, they show you how to write scripts that automate and streamline many common IOS configuration, monitoring, and problem-solving tasks.

The authors walk through the entire script development process, including planning and flowcharting what you want to accomplish, formatting your code, adding comments, and troubleshooting script errors. They also present many downloadable sample scripts, along with practical guidance for adapting them to your own environment.

Whatever your role in managing, monitoring, or securing Cisco IOS networks and equipment, this book will help you get the job done more rapidly and efficiently.

Ray Blair, CCIE No. 7050, is a Cisco vertical solutions architect specializing in large network designs. He has more than 20 years of experience in designing, implementing, and maintaining networks, and maintains three CCIE certifications.

Arvind Durai, CCIE No. 7016, Advanced Services Technical Leader for Cisco, specializes in supporting major Cisco enterprise customers in finance, manufacturing, e-commerce, government, and healthcare. He holds CCIEs in Routing and Switching, and in Security.

John Lautmann, Cisco Software Engineer, has developed and enhanced network management software for twelve years, and holds six patents. He has helped develop new Cisco IOS features ranging from data link switching to IOS Tcl Interpeter and digitally signed Tcl scripts.

  • Automate routine administration tasks you’ve always performed manually
  • Instantly collect and modify IOS router configurations and other data
  • Write Syslog scripts to document failures, monitor network health, collect statistics, and send alarm messages
  • Implement automated network performance measurement using IP SLA
  • Use the Embedded Event Manager’s event detectors, server, and policies to customize device operation
  • Trigger preplanned actions to correct problems as they arise
  • Simplify policy management using the Tcl script refresh feature
  • Protect Tcl script security with digital signatures and PKI
  • Understand how Tcl functions within the Cisco IOS environment
  • Master Tcl syntax and commands through hands-on practice
  • Learn best scripting practices through expert examples
  • Quickly modify this book’s examples for your own environment

This book is part of the Networking Technology Series from Cisco Press®, which offers networking professionals valuable information for constructing efficient networks, understanding new technologies, and building successful careers.

Category: Networking

Covers: Network Administration

$60.00 USA / $72.00 CAN

Table of Contents

Introduction xiv

Chapter 1 The Origin of Tcl 1

    Tcl and Cisco IOS Software 3

        Embedded Event Manager and Tcl 4

        Restriction of Tcl in IOS 4

        Tcl with EEM Support in IOS 5

    Using Tcl Scripts in the Network 8

        Troubleshooting Problems 8

        Monitoring the Network 8

        Adding Intelligence to Cisco IOS Protocols 9

    Summary 9

    References 9

Chapter 2 Tcl Interpreter and Language Basics 11

    Simple Variables in Tcl 12

        Storing Variables 12

        Viewing Variables 13

        The append Command 13

        The incr Command 13

        Representation of Variables in Tcl 14

        Command Substitution 14

        Variable Substitution 15

        Lists 17

        lappend 18

        lindex 18

        linsert 18

        llength 19

        lsearch 19

        lreplace 20

        lrange 20

        lsort 20

    Procedures 21

        for Command 22

        foreach Command 23

        while Command 23

    Arrays 24

    if Command 26

    switch Command 27

    Files 28

    Summary 31

    References 31

Chapter 3 Tcl Functioning in Cisco IOS 33

    Understanding the Tcl Interpreter in Cisco IOS 33

        Using Cisco IOS Exec-Mode Parser in the Tcl Shell 34

        Entering an IOS Command into the Tcl Command Interpreter 35

    Using Tcl to Enter Commands 36

    Copying a Tcl Script to a Cisco IOS Device 38

        Fetching a Cisco IOS Tcl Script from a Remote Device 41

    Using Tcl to Examine the Cisco IOS Device Configuration 41

    Using Tcl to Modify the Router Configuration 43

    Using Tcl with SNMP to Check MIB Variables 44

        Other Uses of SNMP 44

        Enabling SNMP on a Cisco IOS Device 47

        Querying the Configuration of a Cisco IOS Device Using SNMP 48

        Modifying the Configuration of a Cisco IOS Device Using SNMP 51

    Summary 53

    References 53

Chapter 4 Embedded Event Manager (EEM) 55

    EEM Architecture 55

        Policies 56

        EEM Server 56

        Event Detectors 57

    Software Release Support for EEM 60

        Platform and IOS Considerations for EEM 65

    Writing an EEM Applet 66

        Practical Example of an Event Trigger 68

        Using Object Tracking as an Event Trigger 69

        Creating Applet Actions 70

        Examples of EEM Applets 70

        Configuring the IP SLA Sender and Responder 72

        Applet and IP SLA Route Failover Example 74

        Applet That Monitors the Default Route 83

        Applet and Application Failover with a Network Address Translation Example 88

    Using EEM and Tcl Scripts 96

        Programming Policies with Tcl 97

        Tcl Example Used to Check for Interface Errors 98

        Tcl Example Used to Check the CPU Utilization 104

    Summary 110

    References 110

Chapter 5 Advanced Tcl Operation in Cisco IOS 111

    Introduction to the Syslog Protocol 112

    Configuring Syslog Server Parameters in Cisco IOS 113

    Syslog Tcl Script Example 116

        Syslog Tcl Script Sample Output 118

    Sending Syslog Messages to a File 121

        Syslog Server Script Procedures 124

        Syslog Server Script Body 127

    Putting the Syslog Script into Operation 129

    Introduction to Embedded Syslog Manager 130

        Filtering Syslog Messages 130

        ESM Global Variables 134

        Rebuilding a Syslog Message from Its Components 136

        Displaying/Adding ESM Tcl Script Filters 137

    Introduction to Embedded Menu Manager 139

    Using Tcl as a Web Server 144

        Obtaining a Free Web Server Application 147

        Reverse Engineering the Web Server 149

        Creating Your Own Simple Web Page 152

        Creating a Web Page Using IOS show Commands 154

        Adding User Input to the Web Page 157

    Introduction to IP SLA 160

        Adding the IP SLA Measurement to the Web Page 162

        Modifying the Button and Label for User Input 162

        Creating a Tcl Script to Display IP SLA Measurement Results 163

        Putting the New Tcl Scripts into Operation 165

        Reformatting the IP SLA Output for Readability 167

        Automatic Removal and Creation of IP SLA Entries 170

        Displaying the Results of the IP SLA Measurement with Auto-Refresh 174

    Tcl Script Refresh Policy 177

    SNMP Proxy Event Detector 178

    Remote-Procedure Call Requests 179

    Multiple-Event Support for Event Correlation 180

    Using the clear Command 181

    Summary 182

    References 182

Chapter 6 Tcl Script Examples 183

    Creating an Application from Start to Finish 183

        Determine What You Want to Accomplish 183

        Creating a Flowchart 184

        Deciding What the User Interface Should Look Like 185

        Write the Code in Pseudo-Code 187

        Before You Begin 188

        Starting to Program the Application 190

        Configuring the Web Server 190

        Writing Code for the MPLS VPN Script 191

        Configuring HTML 209

        Writing Code for the MPLS CFG Script 216

        Troubleshooting as You Go 228

    Using Tcl to Troubleshoot Network Problems 230

        Monitoring the Console for Events 233

    Creating a Web Application for Remote SNMP Graphing 236

    Summary 241

    References 241

Chapter 7 Security in Tcl Scripts 243

    Introduction to PKI Infrastructure 243

        PKI Prerequisite 244

        Confidentiality with PKI 244

        Digital Signatures with PKI 245

    Using Digital Signatures to Sign a Tcl Script 247

        Step 1: Decide on the Final Tcl Script Contents (Myscript) 248

        Step 2: Generate a Public/Private Key Pair 248

        Step 3: Generate a Certificate with the Key Pair 250

        Step 4: Generate a Detached S/MIME pkcs7 Signature for Myscript Using the Private Key 250

        Step 5: Modify the Format of the Signature to Match the Cisco Style for Signed Tcl Scripts and Append

    It to the End of Myscript 251

    Tcl Script-Failure Scenario 256

    Scaling Tcl Script Distribution 257

    Summary 258

    References 258

Appendix A Cisco IOS Tcl Commands Quick Reference 259

TOC, 9781587059452, 5/17/10

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive:

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020