2086 CHAPTER 113: SNMP CONFIGURATION■ Get operation: NMS gets the value of a certain variable of Agent through thisoperation.■ Set operation: NMS can reconfigure certain values in the Agent MIB(management information base) to make the Agent perform certain tasks bymeans of this operation.■ Trap operation: Agent sends Trap information to the NMS through thisoperation.■ Inform operation: NMS sends Trap information to other NMSs through thisoperation.SNMP Protocol Version Currently, SNMP agents support SNMPv3 and are compatible with SNMPv1 andSNMPv2c.SNMPv1 and SNMPv2c authenticate by means of community name, which definesthe relationship between an SNMP NMS and an SNMP Agent. SNMP packets withcommunity names that did not pass the authentication on the device will simplybe discarded. A community name performs a similar role as a key word and can beused to regulate access from NMS to Agent.SNMPv3 offers an authentication that is implemented with a User-Based SecurityModel (USM for short), which could be authentication with privacy, authenticationwithout privacy, or no authentication no privacy. USM regulates the access fromNMS to Agent in a more efficient way.MIB Overview Management information base (MIB) is a collection of all the objects managed byNMS. It defines the set of characteristics associated with the managed objects,such as the object identifier (OID), access right and data type of the objects.MIB stores data using a tree structure. The node of the tree is the managed objectand can be uniquely identified by a path starting from the root node. As illustratedin the following figure, the managed object B can be uniquely identified by astring of numbers {1.2.1.1}. This string of numbers is the OID of the managedobject B.Figure 624 MIB treeSNMP Configuration As configurations for SNMPv3 differ substantially from those of SNMPv1 andSNMPv2c, their SNMP functionalities will be introduced separately below.Follow these steps to configure SNMPv3:A261521121B
