H3C Technologies H3C S7500E Series Switches - Manual (Page 120)

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z Set operation: The NMS can reconfigure the value of one or more objects in the agent MIB
(Management Information Base) by means of this operation.
z Trap operation: The agent sends traps to the NMS through this operation.
z Inform operation: The NMS sends traps to other NMSs through this operation.
SNMP Protocol Version
Currently, SNMP agents support three protocol versions: SNMPv1, SNMPv2C and SNMPv3.
z SNMPv1 uses community names for authentication, which defines the relationship between
an SNMP NMS and an SNMP agent. SNMP packets with community names that did not
pass the authentication on the device will simply be discarded. A community name
performs a similar role as a password to regulate access from the NMS to the agent.
z SNMPv2c uses community names for authentication. Compatible with SNMPv1, it extends
the functions of SNMPv1. SNMPv2c provides more operation modes such as GetBulk and
InformRequest; 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-based
Security Model (USM). You can set the authentication and privacy functions. The former is
used to authenticate the validity of the sending end of the authentication packets,
preventing access of unauthorized users; the latter is used to encrypt packets between the
NMS and agents, preventing the packets from being intercepted. USM ensures a more
secure communication between SNMP NMS and SNMP agent by authentication with
privacy, authentication without privacy, or no authentication no privacy.
Successful interaction between an NMS and the agents requires consistency of SNMP versions
configured on them. You can configure multiple SNMP versions for an agent to interact with
different NMSs.
MIB Overview
Any 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
hierarchy of the objects and a set of characteristics associated with the managed objects, such
as the object identifier (OID), access right and data type. Each agent has its own MIB. An NMS
can read or write the managed objects in the MIB. The relationship between an NMS, agent and
MIB is shown in Figure 6-1 .
Figure 6-1 Relationship between an NMS, agent and MIB
MIB stores data using a tree structure. Each node of the tree represents a managed object that
can be uniquely identified by a path starting from the root node. As illustrated in the following