TcL Scripting for Cisco IOS: (Networking Technology)

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. 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.

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

About the Author :
Ray Blair, CCIE No. 7050, is a Vertical Solutions Architect and has been with Cisco Systems for more than 10 years, working primarily with large network designs. He has almost 22 years of experience with designing, implementing, and maintaining networks that have included nearly all networking technologies. During the early stages of his career, he wrote many applications using Assembly language and C. Mr. Blair maintains three CCIE certifications in Routing and Switching, Security, and Service Provider. He is also a Certified Information Systems Security Professional (CISSP) and coauthor of the Cisco Secure Firewall Services Module book.   Arvind Durai, CCIE No. 7016, is an Advanced Services Technical Leader for Cisco Systems. His primary responsibility in the past 10 years has been in supporting major Cisco customers in the enterprise sector, including financial, manufacturing, e-commerce, state government, utility (smart grid networks) and health-care sectors. Some of his focuses have been on security, multicast, network virtualization, and he has authored several white papers and design guides in various technologies. He has leveraged Embedded Event Manager (EEM) and Tool Command Language (Tcl) scripts in various customer designs. Mr. Durai maintains two CCIE certifications: Routing and Switching, and Security. He holds a Bachelor of Science degree in electronics and communication, a master’s degree in electrical engineering (MS), and master’s degree in business administration (MBA), and is a coauthor of Cisco Secure Firewall Services Module.   John Lautmann is a Software Engineer for Cisco Systems. He has developed and enhanced network management software for nearly 14 years. Before joining Cisco, he held positions in customer support and software testing. With six networking patents, John has been involved in the development of new Cisco IOS features such as data-link switching, syslog, configuration rollback and archiving, IOS Tcl interpreter, digitally signed Tcl scripts, and Multiprotocol Label Switching (MPLS) ping and trace. Mr. Lautmann holds a Bachelor of Science degree in computer science and master’s degrees in both business and engineering.