MIBs fall into the following two types:
Public MIBs
Defined by RFCs, the public MIBs, for example, OSPF-MIB (RFC 1850) and BGP4-MIB (RFC 1657), allow the structure design of common protocols and the standardization of interfaces. Manufacturers design and offer SNMP interfaces according to the specifications defined in RFC.
Private MIBs
They are the supplement of the public MIBs. Some enterprises need to develop private protocols or special functions. The private MIBs are designed to enable the SNMP interface to manage such protocols or functions. They also help the NMS provided by the third party to manage devices.