Perl for System Administration

Appendix E. The Twenty-Minute SNMP Tutorial

The Simple Network Management Protocol (SNMP) is the ubiquitous protocol used to manage devices on a network. Unfortunately, as we metioned at the beginning of Chapter 10, 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 that you have a management station that polls an SNMP agent running on a remote device for information. The agent can also be instructed to signal the management station if an important condition arises (like a counter exceeding a threshold). When we programmed in Perl in Chapter 10, 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. There have been seven versions of the protocol (SNMPv1, SNMPsec, SNMPv2p, SNMPv2c, SNMPv2u, SNMPv2* and SNMPv3) proposed. v1 is the only one that has been 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 one of four primitive types: integers, strings, object identifiers (more on this in a moment), or null values. And just like Perl, in SNMP a set of related variables can be grouped ...