H3C Technologies H3C SecPath F1000-E - Manual (Page 152)

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• Trap operation: The agent sends traps to the NMS through this operation.
• 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.
• 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.
• 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.
• 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.
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 1 .
Figure 1 Relationship between an NMS, agent and MIB
A MIB stores data by 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 figure, the
managed object B can be uniquely identified by a string of numbers {1.2.1.1}. This string is the OID of the
managed object B.