SNMP stands for Simple Network Management Protocol. At its heart, SNMP is a set of rules that allows a computer to get statistics from another computer across the Internet.
Computers keep track of various statistics that measure what they're doing. For example, routers might keep track of the number of bytes, packets, and errors transmitted and received on each interface (port). Web servers might keep a tally of the number of hits they have received. Many kinds of equipment have configuration information available through SNMP.
Each of these pieces of information (packet statistics, page hits, configuration) is kept in a database described by a Management Information Base or MIB. There are a many different MIBs, each describing many different aspects of a computer's operation.
The values that can be retrieved from a MIB are called MIB objects. These objects are defined in the device's MIB. Each MIB object is named by an Object Identifier (OID), usually expressed in numbers separated by dots ("."), like this:
1.3.6.1.xxxx.x.x.x.x...
For example, the MIB-II (pronounced, "MIB two") has an object that indicates the number of interfaces (ports) in a router. It's called the "ifNumber", and its OID is
1.3.6.1.2.1.2.1.0
Intermapper, as well as many other network monitoring tools, can query a device for its MIB objects and display the results. When a device receives a SNMP Get-Request for this ifNumber OID, it responds with the count of interfaces.
Note: The trailing ".0" in the example above is technically part of the OID. Although you will often see OIDs written without it, Intermapper requires that it be present wherever you enter an OID.
