TCP/IP MIB Modules and Object Groups
(Page 3 of 4)
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.
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 220.127.116.11.2.1 name subtree):
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.
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