McDATA 316095-B21 - StorageWorks Edge Switch 2/24, Руководство пользователя

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1
Network Management using SNMP
1-3
Introduction to SNMP
• Set–A manager can change the variables in the agent by sending
this single command. This command is used to change the
management data.
• GetBulk–This command is used by the manager to retrieve
voluminous data from a large table in the agent.
• Trap–An Agent uses this command to inform the manager about
some unusual events. Refer to
Traps and Their Purpose
on page 1-9.
• Inform– This command is used by a manager to send alert to
another manager.
Figure 1-1
SNMP Commands and Responses
Why Variables exist
In a Managed
Device
Variables are the means by which devices like switches and directors
keep track of and control their performance apart from providing
access about their performance to network managers. A simple
example of a variable’s use is to set a port offline and turn the port
back on. Some variables just hold values that indicate status (for
example error counts). SNMP allows the network managers to have
access to some of the same variables for network management.
For purposes of the following explanation, an object is a data variable
that represents an attribute of a managed device.
How SNMP Changes
Variables in a
Managed Device
An agent has an interface to the actual object being managed
(
Figure 1-2 on page 1-4). The agent understands SNMP and translates
between the manager and the object. Each SNMP element manages
specific objects. Each object has an identifier, OID. Objects may be
GetRes
ponse
PDU
GetRe
quest
PDU
Get Values
NMS Switch
SetRes
ponse
PDU
SetRe
quest
PDU
Set Values
GetRespo
nse PDU
GetNextR
equest
PDU
Get Next Values
NMS Switch
Trap P
DU
Send Trap