SNMP Reference Guide

Introduction 35
SNMP Management Information Base Object Identifiers
Each data class within a Management Information Base (MIB) is defined by
an Object Identifier (OID). OIDs are unique across all MIBs. An OID
consists of a series of digits separated by periods. The OID functions in a
similar fashion to a phone number. The phone number 011-512-471-0000
uniquely identifies a single phone. The phone number can be broken down
into a number of components to uniquely identify a phone. The first
component, 011, is the country code for the United States. The second
component, 512, identifies the area code for central Texas. The third
component, 471, is the phone exchange for a large state university in the city
of Austin. The final component, 0000, is the main switchboard.
There are two main differences between the phone number example and an
actual OID. The first difference is that there are many more components in
an OID, up to 128. The combination of these components is called an OID
prefix. The second difference is that OIDs support the concept of indexes or
keys. The OID prefix specifies the data class but does not specify an instance of
the data within the class. Indexes can be used to identify the instances of a data
class. These indexes are referred to as the OID suffix.
The assignment of values for each OID prefix component can be illustrated
by using a tree structure. The following is an example of an OID assignment:
ROOT
CCITT(0)
ISO(1)
ORG(
3)
DOD(
6)
INTERNET(
1)
MGMT(2)
MIB(1)
EXPERIMENTAL(3)
PRIVATE(
4)
ENTERPRISES(
1)
DELL
(
674)
SNMPv2(6)
book.book Page 35 Tuesday, February 28, 2012 2:19 PM