Preface

The Simple Network Management Protocol (SNMP) is an Internet-standard protocol for managing devices on IP networks. Many kinds of devices support SNMP, including routers, switches, servers, workstations, printers, modem racks, and uninterruptible power supplies (UPSs). The ways you can use SNMP range from the mundane to the exotic: it's fairly simple to use SNMP to monitor the health of your routers, servers, and other pieces of network hardware, but you can also use it to control your network devices and even send pages or take other automatic action if problems arise. The information you can monitor ranges from relatively simple and standardized items, like the amount of traffic flowing into or out of an interface, to more esoteric hardware- and vendor-specific items, like the air temperature inside a router.

Given that there are already a number of books about SNMP in print, why write another one? Although there are many books on SNMP, there's a lack of books aimed at the practicing network or system administrator. Many books cover how to implement SNMP or discuss the protocol at a fairly abstract level, but none really answers the network administrator's most basic questions: How can I best put SNMP to work on my network? How can I make managing my network easier?

We provide a brief overview of the SNMP protocol in Chapter 2, "A Closer Look at SNMP" then spend a few chapters discussing issues such as hardware requirements and the sorts of tools that are available for use with SNMP. However, the bulk of this book is devoted to discussing, with real examples, how to use SNMP for system and network administration tasks.

Most newcomers to SNMP ask some or all of the following questions:

What exactly is SNMP?
How can I, as a system or network administrator, benefit from SNMP?
What is a MIB?
What is an OID?
What is a community string?
What is a trap?
I've heard that SNMP is insecure. Is this true?
Do any of my devices support SNMP? If so, how can I tell if they are configured properly?
How do I go about gathering SNMP information from a device?
I have a limited budget for purchasing network-management software. What sort of free/open source software is available?
Is there an SNMP Perl module that I can use to write cool scripts?

This book answers all these questions and more. Our goal is to demystify SNMP and make it more accessible to a wider range of users.

0.1. Audience for This Book

This book is intended for system and network administrators who could benefit from using SNMP to manage their equipment but who have little or no experience with SNMP or SNMP applications. In our experience almost any network, no matter how small, can benefit from using SNMP. If you're a Perl programmer, this book will give you some ideas about how to write scripts that use SNMP to help manage your network. If you're not a Perl user you can use many of the other tools we present, ranging from Net-SNMP (an open source collection of command-line tools) to Hewlett Packard's OpenView (a high-end, high-priced network-management platform).