A MIB is a tree structured, extensible database of objects that describe devices within a network and how to monitor and manipulate them. A MIB for a particular device is likely to be based on and include (IMPORT) the descriptions of other standard MIBs. The device specific MIB enhances the description with attributes that are specific to its function. Referring to Figure 9.116, what is formed is a hierarchy of object descriptions, such that each branch or leaf (end point) may be uniquely identified by an object identifier (OID). Many definitions have common "standard" elements. These are contained within the mgmt branch (1.3.6.1.2) most typically under the (not shown) mib/mib-2 branch (1.3.6.1.2.1). In Figure 0.1 below, iso.org.dod.internet.private, is OID 1.3.6.1.4. Below the private branch are enterprises (not shown), which constitute private enterprises. Enterprise numbers are allocated and managed by the Internet Assigned Numbers Authority (IANA) to ensure uniqueness. The enterprise number for Colfax Corporation is 30828. Thus, the OID that specifies the Colfax branch would be 1.3.6.1.4.1.30828. Any Colfax specific MIB information will appear under this branch. This is not where physical Colfax devices are, just the description about those it manufactures. When a particular device responds to an SNMP query for its OID, the response indicates what it is, because the OID can be looked up in the MIB. Once this is done, all of the information it has available is known as well as how it may be modified.
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