Management Information Base

Article
06/30/2006

A Management Information Base (MIB) is a map of the hierarchical order of all of the managed objects or MIB variables. Each system in a network (workstation, server, router, bridge, and so on) maintains a MIB that reflects the status of the managed resources at that system. A MIB allows the SNMP manager to retrieve and modify data that is maintained by an agent. When it receives a request for a value from the manager, the SNMP master agent passes the request to the extension-agent DLL, which implements the appropriate MIB to retrieve the value that was requested.

A MIB consists of a collection of MIB variables that are managed by the SNMP manager. Each variable within a MIB is referenced with a unique OID. An OID refers to the location of a managed object within the MIB namespace. OIDs are arranged in a tree-like structure that begins with a root and expands downwards into branches. Each point in a MIB tree is known as a node. In a network that is managed by SNMP, access is provided only to the leaf nodes. The value of each OID consists of a sequence of integers. The dotted numeric string representation of an OID separates its subidentifiers with periods; for example, 1.2.3.4.5.6. A MIB variable is referenced by its OID, as well as by its instance identifier, such as INTEGER, STRING, COUNTER, and GAUGE.

The following code example shows a MIB object for the Toaster MIB.

toasterModelNumber OBJECT-TYPE
    SYNTAX  DisplayString
    ACCESS  read-only
    STATUS  mandatory
    DESCRIPTION 
            "The name of the model of the toaster. For instance,
            Radiant Automatic."
    ::= {toaster 2}

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