Cisco Cisco MDS 9000 NX-OS Software Release 4.1 Referencia técnica
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SNMP has been updated twice since its inception. SNMPv1 is the initial version of the protocol.
SNMPv2 added support for 64-bit counters, and SNMPv3 added robust security for access,
authentication, and encryption of managed data.
SNMPv2 added support for 64-bit counters, and SNMPv3 added robust security for access,
authentication, and encryption of managed data.
SNMP Traps and Informs
You can configure the Cisco MDS 9000 Family switch to send notifications to SNMP managers when
particular events occur. You can send these notifications as traps or inform requests. Traps are unreliable
because the receiver does not send any acknowledgment when it receives a trap. The sender cannot
determine if the trap was received. However, an SNMP manager that receives an inform request
acknowledges the message with an SNMP response. If the sender never receives a response, the inform
request can be sent again. Thus, informs are more likely to reach their intended destinations.
particular events occur. You can send these notifications as traps or inform requests. Traps are unreliable
because the receiver does not send any acknowledgment when it receives a trap. The sender cannot
determine if the trap was received. However, an SNMP manager that receives an inform request
acknowledges the message with an SNMP response. If the sender never receives a response, the inform
request can be sent again. Thus, informs are more likely to reach their intended destinations.
Notifications may contain a list of MIB variables or varbinds that clarify the status being relayed by the
notification. The list of varbinds associated with a notification is included in the notification definition
in the MIB. In the case of standard MIBs, Cisco has enhanced some notifications with additional
varbinds that further clarify the cause of the notification. See the
notification. The list of varbinds associated with a notification is included in the notification definition
in the MIB. In the case of standard MIBs, Cisco has enhanced some notifications with additional
varbinds that further clarify the cause of the notification. See the
for an example of this in the IF-MIB.
Table 1
SNMP Operations
Operation
Description
get-request
Retrieves a value from a specific variable.
get-next-request
Retrieves the value following the named variable. Often used to retrieve variables
from within a table.
from within a table.
1
1.With this operation, an SNMP manager does not need to know the exact variable name. A sequential search finds the next variable
from within the MIB.
get-bulk
2
2.The get-bulk and inform commands are not a part of SNMPv1.
Retrieves large blocks of data, such as multiple rows in a table, which would
otherwise require the transmission of many small blocks of data.
otherwise require the transmission of many small blocks of data.
set-request
Stores a value in a specific variable.
response
Replies to the above commands sent by an NMS and to the informs sent by an
agent.
agent.
trap
Sends an unsolicited message by an SNMP agent to an SNMP manager indicating
that some event has occurred.
that some event has occurred.
inform
2
Sends an unsolicited message by an SNMP agent to an SNMP manager indicating
that some event has occurred. Differs from a trap in that an acknowledgement is
required from the manager.
that some event has occurred. Differs from a trap in that an acknowledgement is
required from the manager.