Automating System Administration with Perl, 2nd Edition

Appendix G. The 20-Minute SNMP Tutorial

The Simple Network Management Protocol (SNMP) is the ubiquitous protocol used to manage devices on a network. Unfortunately, as mentioned at the beginning of Chapter 12, SNMP is not a particularly simple protocol (despite its name). This longish tutorial will give you the information you need to get started with version 1 of SNMP.

SNMP is predicated on the notion of a management station polling SNMP agents running on remote devices for information. An agent can also signal the management station if an important condition arises, such as a counter exceeding a threshold. When we programmed SNMP in Perl in Chapter 12, we essentially acted as a management station, polling the SNMP agents on other network devices.

We’re going to concentrate on version 1 of SNMP in this tutorial. Seven versions of the protocol (SNMPv1, SNMPsec, SNMPv2p, SNMPv2c, SNMPv2u, SNMPv2*, and SNMPv3) have been proposed; v1 is the one that has been most widely implemented and deployed, though v3 is expected to eventually ascend thanks to its superior security architecture.

Perl and SNMP both have simple data types. Perl uses a scalar as its base type. Lists and hashes are just collections of scalars in Perl. In SNMP, you also work with scalar variables. SNMP variables can hold any of four primitive types: integers, strings, object identifiers (more on this in a moment), or null values. And just like in Perl, in SNMP a set of related variables can be grouped together to form ...