OID

Ok, Let’s start with the OID.  OID stands for Object ID or Object Identifier.  Basically an address to reach an object.

OIDs can either be represented as a numeric, a tree of numbers, or textual, a tree of names

Examples:

• Numbers: 1.3.6.1.2.1.1.3
• Names: iso.org.dod.internet.mgmt.mib.system.sysUpTime

Note: When referencing OIDs going forward I will used the following notation:

iso(1).org(3).dod(6).internet(1).mgmt(2).mib(1).system(1).sysUpTime(3)

The two trees that are most often used for network monitoring are:

• iso(1).org(3).dod(6).internet(1).mgmt(2)
• iso(1).org(3).dod(6).internet(1).private(4).enterprises(1)

All trees under iso(1).org(3).dod(6).internet(1).mgmt(2) are defined and published via RFC 

All trees under iso(1).org(3).dod(6).internet(1).private(4).enterprises(1) are assigned to companies by the IANA.  These companies then create their own sub-trees.  These sub-trees are defined in MIB files that are published by these companies.  We will cover MIB files in another post  Some example sub-trees to enterprises(1) are IBM(2), ciscoSystems(9), Juniper Networks, Inc.(2636), Netgear(4526), PALO ALTO NETWORKS(25461)

So you have the OID (address) that you want, but what is an object and how do I use it.

An object is a generic term for a container. This object can be one of many different types.  There are 11 object types defined in the applicable RFC for SNMPv1 that is current as of this writing:

INTEGER, OCTET STRING, OBJECT IDENTIFIER, NULL, NetworkAddress, IpAddress, Counter, Gauge, TimeTicks, Opaque

For those of you counting, that is only 10.  The 11th object type is SEQUENCE.  It is a object that contains multiple entries of one of the object types above.

There are 12 object types defined in the applicable RFC for SNMPv2 that is current as of this writing:

INTEGER and INTEGER32 (seems to me like 2, but they are defined together), OCTET STRING, OBJECT IDENTIFIER, BITS construct, IpAddress, Counter32, Gauge32, TimeTicks, Opaque, Counter64, Unsigned32, Conceptual Tables (SEQUENCE OF) 

In addition to these RFC defined object types, new object types can be defined as needed.  These are defined by companies in MIB files that they publish.