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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)
           9  TCP/IP Network Management Framework and Protocols (SNMP and RMON)
                9  TCP/IP Structure of Management Information (SMI) and Management Information Bases (MIBs)

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TCP/IP MIB Object Descriptors and Identifiers and the Object Name Hierarchy and Name Notation
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TCP/IP Simple Network Management Protocol (SNMP) Protocol
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TCP/IP MIB Modules and Object Groups
(Page 3 of 4)

MIB Modules

What's most conspicuous about Table 208 are the groups that are not in it. There are no groups for most of the other TCP/IP protocols, nor any for variables that might be needed for specific hardware types. For example, most hosts will have a network card in them using a layer two protocol like Ethernet or Token Ring; how does a manager check or control the operation of this hardware? What about newer routing protocols like OSPF or BGP? How about objects related to running the Domain Name System?

Updating the MIB document constantly would have been impractical. Instead, in SNMPv2, the Management Information Base was changed from a single document to a group of documents. The basic organization into groups of objects was retained, but instead of all groups being in the same standard, they are divided into multiple standards. A method was also defined for how to create MIB modules that describe new groups of objects specific to a particular technology. A list of these modules is maintained by IANA, the organization that maintains all of these sorts of numbers.

On The Web: The current list of SNMP MIB modules can be found here:

The use of MIB modules makes putting SNMP support into a device somewhat like “going shopping”. The basic groups common to all devices are incorporated into each device, and then other modules/groups are used as needed. Table 209 provides a brief selection of MIB modules to give you an idea of what is out there, also showing the module's group number (within the name subtree):

Table 209: Some Common SNMP MIB Modules

MIB Module Name

Group Number




Objects related to the Open Shortest Path First protocol.



Objects related to the Border Gateway Protocol.



Objects used as part of Remote Network Monitoring (RMON), which we'll examine later in this chapter.



Objects related to IEEE 802.3 (Ethernet) repeaters.



Objects used as part of version 2 of the Routing Information Protocol.



Objects related to IEEE 802.3 (Ethernet) medium attachment units.



Ethernet-like generic objects.



Mobile IP objects.



Internet Protocol objects for SNMPv2.



Transmission Control Protocol objects for SNMPv2.



User Datagram Protocol objects for SNMPv2.

There are of course, many, many more. The last three entries in the table above might seem a bit confusing, since there are already groups for IP, TCP and UDP in the first table above. The reason for these is that when the new modular architecture for MIB objects was created in SNMPv2, the definition of objects for the individual protocols that was part of the “one document” in SNMPv1 was separated out into individual MIB documents for consistency, and to allow them to be updated independently. In fact, the “base” SNMPv2 and SNMPv3 MIB documents now only define objects in the system and snmp groups.

Key Concept: MIB objects created early in SNMP’s history were organized into MIB object groups that reside within mib(1) subtree, starting with identifier code As the popularity of TCP/IP grew, it became impractical to centrally-define all MIB objects, so sets of objects particular to different hardware devices are now specified in MIB modules.

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