through a single error code in SNMPv1. Error return codes now report the error type. Three kinds of exceptions
are also reported: no such object exceptions, no such instance exceptions, and end of MIB view exceptions.
SNMPv3 is a security model. A security model is an authentication strategy that is set up for a user and the
group in which the user resides. A security level is the permitted level of security within a security model. A
combination of a security model and a security level will determine which security mechanism is employed
when an SNMP packet is handled. See Table 38: SNMP Security Models and Levels, on page 360 for a list
of security levels available in SNMPv3. The SNMPv3 feature supports RFCs 3411 to 3418.
You must configure the SNMP agent to use the version of SNMP supported by the management station. An
agent can communicate with multiple managers; for this reason, you can configure the Cisco IOS-XR software
to support communications with one management station using the SNMPv1 protocol, one using the SNMPv2c
protocol, and another using SMNPv3.
Comparison of SNMPv1, v2c, and v3
SNMP v1, v2c, and v3 all support the following operations:
• get-request—Retrieves a value from a specific variable.
• get-next-request—Retrieves the value following the named variable; this operation is often used to
retrieve variables from within a table. With this operation, an SNMP manager does not need to know
the exact variable name. The SNMP manager searches sequentially to find the needed variable from
within the MIB.
• get-response—Operation that replies to a get-request, get-next-request, and set-request sent by an NMS.
• set-request—Operation that stores a value in a specific variable.
• trap—Unsolicited message sent by an SNMP agent to an SNMP manager when some event has occurred.
Table 37: SNMPv1, v2c, and v3 Feature Support, on page 359 identifies other key SNMP features supported
by the SNMP v1, v2c, and v3.
Table 37: SNMPv1, v2c, and v3 Feature Support
SNMP v3SNMP v2cSNMP v1Feature
YesYesNoGet-Bulk Operation
Yes (No on the
Cisco IOS XR software)
Yes (No on the
Cisco IOS XR software)
NoInform Operation
YesYesNo64 Bit Counter
YesYesNoTextual Conventions
YesNoNoAuthentication
YesNoNoPrivacy (Encryption)
YesNoNoAuthorization and Access
Controls (Views)
Cisco ASR 9000 Series Aggregation Services Router System Management Configuration Guide, Release 5.1.x
359
Implementing SNMP
SNMP Versions
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