SNMP Basics

Quoted from:  http://www.debianhelp.co.uk/linuxoids.htm
SNMP Basics

SNMP stands for Simple Network Management Protocol and consists of three key components: managed devices, agents, and network-management systems (NMSs). A managed device is a node that has an SNMP agent and resides on a managed network. These devices can be routers and access server, switches and bridges, hubs, computer hosts, or printers. An agent is a software module residing within a device. This agent translates information into a compatible format with SNMP. An NMS runs monitoring applications. They provide the bulk of processing and memory resources required for network management.

MIBs, OIDs Overview

MIB stands for Management Information Base and is a collection of information organized hierarchically. These are accessed using a protocol such as SNMP. There are two types of MIBs: scalar and tabular. Scalar objects define a single object instance whereas tabular objects define multiple related object instances grouped in MIB tables.
MIB files for specific devices or systems can be downloaded from here

OIDs or Object Identifiers uniquely identify manged objects in a MIB hierarchy. This can be depicted as a tree, the levels of which are assigned by different organizations. Top level MIB object IDs (OIDs) belong to different standard organizations. Vendors define private branches including managed objects for their own products.

Here is a sample structure of an OID

Iso (1).org(3).dod(6).internet(1).private(4).transition(868).products(2).chassis(4).card(1).slotCps(2)­
.­cpsSlotSummary(1).cpsModuleTable(1).cpsModuleEntry(1).cpsModuleModel(3).3562.3

Most of the people may be looking for OID's for Linux OID's for CPU,Memory and Disk Statistics for this first you need to install SNMP server and clients. If you want to install SNMP server and client installation in linux check here
 CPU  Statistics

        Load
               1 minute Load: .1.3.6.1.4.1.2021.10.1.3.1
               5 minute Load: .1.3.6.1.4.1.2021.10.1.3.2
               15 minute Load: .1.3.6.1.4.1.2021.10.1.3.3

       CPU
               percentage of user CPU time:    .1.3.6.1.4.1.2021.11.9.0
               raw user cpu time:                  .1.3.6.1.4.1.2021.11.50.0
               percentages of system CPU time: .1.3.6.1.4.1.2021.11.10.0
               raw system cpu time:              .1.3.6.1.4.1.2021.11.52.0
               percentages of idle CPU time:   .1.3.6.1.4.1.2021.11.11.0
               raw idle cpu time:                   .1.3.6.1.4.1.2021.11.53.0
               raw nice cpu time:                  .1.3.6.1.4.1.2021.11.51.0

Memory Statistics

               Total Swap Size:                .1.3.6.1.4.1.2021.4.3.0
               Available Swap Space:         .1.3.6.1.4.1.2021.4.4.0
               Total RAM in machine:          .1.3.6.1.4.1.2021.4.5.0
               Total RAM used:                  .1.3.6.1.4.1.2021.4.6.0
               Total RAM Free:                   .1.3.6.1.4.1.2021.4.11.0
               Total RAM Shared:                .1.3.6.1.4.1.2021.4.13.0
               Total RAM Buffered:              .1.3.6.1.4.1.2021.4.14.0
               Total Cached Memory:           .1.3.6.1.4.1.2021.4.15.0

Disk Statistics

       The snmpd.conf needs to be edited. Add the following (assuming a machine with a single '/' partition):

                               disk    /       100000  (or)
                               includeAllDisks 10% for all partitions and disks

       The OIDs are as follows

               Path where the disk is mounted:                 .1.3.6.1.4.1.2021.9.1.2.1
               Path of the device for the partition:            .1.3.6.1.4.1.2021.9.1.3.1
               Total size of the disk/partion (kBytes):        .1.3.6.1.4.1.2021.9.1.6.1
               Available space on the disk:                      .1.3.6.1.4.1.2021.9.1.7.1
               Used space on the disk:                           .1.3.6.1.4.1.2021.9.1.8.1
               Percentage of space used on disk:             .1.3.6.1.4.1.2021.9.1.9.1
               Percentage of inodes used on disk:            .1.3.6.1.4.1.2021.9.1.10.1

V3 Sample 
# snmpget -v 3 -l AuthNoPriv -u cactiuser -A <password> 37.15.140.13 .1.3.6.1.4.1.2021.4.5.0