Vendors do not have to implement all the MIBs SNMP provides, but SNMP-manageable devices must support at least MIB-II. It also behooves the vendors to implement some of the more useful MIBs, as well as their own private MIBs, since the ability to manage a product effectively using SNMP is an increasingly important selling point.
You can find a few examples of these standard MIBs in Chapter 1, "What Is SNMP?".
Additionally, if the product is SNMPv2 and SNMPv3 compatible, it must support the following operations:
Vendors can choose to support SNMPv1, SNMPv2, SNMPv2, or all three. An SNMP agent that supports two versions of SNMP is called "bilingual." In recent years, this was restricted to devices supporting SNMPv1 and SNMPv2. Now a device can support all three versions, which technically makes it trilingual. It is possible for an agent to speak all versions of SNMP because SMIv2 is a superset of SMIv1, and SMIv2 is used, for the most part, with SNMPv3.
Supporting these operations, however, is only one piece to the puzzle of providing a manageable product. The other piece is providing a private MIB that is comprehensive enough to give network managers the information they need to manage their networks intelligently. In today's complex network environments, it does not pay to purchase equipment that has a minimal or poorly implemented private MIB. For instance, it is important to measure ambient temperature inside devices such as routers, hubs, and switches. Cisco and others provide this information via their private MIBs; other vendors do not. If you're in the process of purchasing a high-end router, you might want to look into the vendors' private MIBs to see which vendors provide more relevant information.
Another factor that affects vendor MIB support is product definition. Concord Communications (vendors of an SNMP agent for Unix and Windows) will probably not support the RS-232 MIB (RFC 1659), since their product is geared toward providing system- and application-management information. 3Com, on the other hand, implemented this MIB for their line of Dual Speed Hubs, since these hubs have RS-232 ports.
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