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Figure 28 MIB tree
A MIB view represents a set of MIB objects (or MIB object hierarchies) with certain access privileges
and is identified by a view name. The MIB objects included in the MIB view are accessible while
those excluded from the MIB view are inaccessible.
A MIB view can have multiple view records each identified by a
view-name oid-tree
pair.
You control access to the MIB by assigning MIB views to SNMP groups or communities.
For an NMS to identify the device model of each device, SNMP uses the device OID to uniquely
identify a device. Devices of the same model share the same OID.
An IRF fabric does not have an independent OID. When an NMS requests the OID of an IRF fabric,
the IRF fabric sends the OIDs of all IRF member devices.
SNMP operations
SNMP provides the following basic operations:
•
Get
—NMS retrieves the SNMP object nodes in an agent MIB.
•
Set
—NMS modifies the value of an object node in an agent MIB.
•
Notification
—SNMP agent sends traps or informs to report events to the NMS. The difference
between these two types of notification is that informs require acknowledgment but traps do not.
Traps are available in SNMPv1, SNMPv2c, and SNMPv3, but informs are available only in
SNMPv2c and SNMPv3.
Protocol versions
SNMPv1, SNMPv2c, and SNMPv3 are supported in non-FIPS mode. Only SNMPv3 is supported in
FIPS mode. An NMS and an SNMP agent must use the same SNMP version to communicate with
each other.
•
SNMPv1
—Uses community names for authentication. To access an SNMP agent, an NMS
must use the same community name as set on the SNMP agent. If the community name used
by the NMS differs from the community name set on the agent, the NMS cannot establish an
SNMP session to access the agent or receive traps from the agent.
•
SNMPv2c
—Uses community names for authentication. SNMPv2c is compatible with SNMPv1,
but supports more operation types, data types, and error codes.
•
SNMPv3
—Uses a user-based security model (USM) to secure SNMP communication. You can
configure authentication and privacy mechanisms to authenticate and encrypt SNMP packets
for integrity, authenticity, and confidentiality.
Access control modes
SNMP uses the following modes to control access to MIB objects:
