Which of the following SNMP actions are used by an NMS to extract information from an SNMP agent? (Select2 choices.)
A.
get
B.
getNext
C.
set
D.
inform
E.
trap
Explanation:
The get and getNext actions are used by a network management station (NMS) to extract information from a
Simple Network Management Protocol (SNMP) agent. SNMP is a protocol that an NMS can use to
communicate with an agent in the same community. If the NMS and the agent do not share the same
community string, the NMS is not permitted to communicate with the agent. SNMP communities can be
configured to be either readonly or readwrite. Readonly communities enable an NMS to retrieve Management
Information Base (MIB) data from a community, whereas readwrite communities enable an NMS to modify and
retrieve MIB data. If the NMS is authorized to communicate with the agent of a readonly community, the NMS
can take any of the following actions:
get – request a particular item from the MIB
getNext – request the next sequential item from the MIB
getBulk – request several sequential items from the MIB
By contrast, if the NMS is authorized to communicate with the agent of a readwrite community, the NMS can
take any of the following actions:
get – request a particular item from the MIB
getNext – request the next sequential item from the MIB
getBulk – request several sequential items from the MIB
set – modify an item in the MIB
The SNMP agent typically accumulates statistical data regarding the number and type of SNMP requests and
responses it has processed. For example, on Cisco routers, you can use the show snmp command to display
the accumulated SNMP statistics, as shown in the following sample output:
Chassis: 4279256517
1230 SNMP packets input
2 Bad SNMP version errors
5 Unknown community name
4 Illegal operation for community name supplied
0 Encoding errors
0 Number of requested variables
0 Number of altered variables
680 Getrequest PDU
479 Getnext PDUs
60 Setrequest PDUs
0 Input queue packet drops (Maximum queue size 1000)
1230 SNMP packets output
0 Too big errors (Maximum packet size 1500)
No such name errors
Bad values errors
0 General errors
762 Response PDUs 0 Trap PDUs
SNMP logging: disabled
The sample output indicates the number of get, getNext, and set requests that have been received by the
router as well as statistics on the number of various types of SNMP packets the router has sent in response to
NMS queries. For example, the Illegal operation for community name supplied field in the sample output
indicates that four SNMP packets requested an operation that was not allowed for the associated community,
such as a set request for a community that permits only get requests. In addition, the Unknown communityname field indicates that five SNMP packets were received with unknown community strings.
The trap and inform actions are not used by an NMS to extract information from an SNMP agent. Instead, the
trap and inform actions are used by an SNMP agent to alert an NMS when a particular threshold has been
exceeded:
trap – send to the NMS an alert that does not require an acknowledgment
inform – send to the NMS an alert that requires an acknowledgment
Although the inform action is more reliable than the trap action, the inform action can consume additional
resources. The inform action can be sent multiple times until the NMS acknowledges it. In addition, the agent
stores the data from the inform action in local memory until the NMS acknowledges the receipt of the
notification.Cisco: Configuring SNMP Support: SNMP Get