1-2z Inform operation: The NMS sends traps to other NMSs through this operation.SNMP Protocol VersionCurrently, SNMP agents support SNMPv3 and are compatible with SNMPv1 and SNMPv2c.z SNMPv1 uses community names for authentication, which defines the relationship between anSNMP NMS and an SNMP agent. SNMP packets with community names that did not pass theauthentication on the device will simply be discarded. A community name performs a similar role asa password to regulate access from the NMS to the agent.z SNMPv2c uses community names for authentication. Compatible with SNMPv1, it extends thefunctions of SNMPv1. SNMPv2c provides more operation modes such as GetBulk andInformRequest; it supports more data types such as Counter64 and provides various error codes,thus being able to distinguish errors in more detail.z SNMPv3 offers an authentication mechanism that is implemented based on the User-basedSecurity Model (USM). You can set the authentication and privacy functions. The former is used toauthenticate the validity of the sending end of the authentication packets, preventing access ofunauthorized users; the latter is used to encrypt packets between the NMS and agents, preventingthe packets from being intercepted. USM ensures a more secure communication between SNMPNMS and SNMP agent by authentication with privacy, authentication without privacy, or noauthentication no privacy.Successful interaction between an NMS and the agents requires consistency of SNMP versionsconfigured on them. You can configure multiple SNMP versions for an agent to interact with differentNMSs.MIB OverviewAny managed resource can be identified as an object, which is known as the managed object.Management Information Base (MIB) is a collection of all the managed objects. It defines the hierarchyof the objects and a set of characteristics associated with the managed objects, such as the objectidentifier (OID), access right and data type. Each agent has its own MIB. An NMS can read or write themanaged objects in the MIB. The relationship between an NMS, agent and MIB is shown in Figure 1-1.Figure 1-1 Relationship between an NMS, agent and MIBMIB stores data using a tree structure. Each node of the tree represents a managed object that can beuniquely identified by a path starting from the root node. As illustrated in the following figure, themanaged object B can be uniquely identified by a string of numbers {1.2.1.1}. This string is the OID ofthe managed object B.
