FW 07.00.00/HAFM SW 08.06.00 McDATA E/OS SNMP Support Manual (620-000131-620, April 2005)

1
SNMP Management
1-3
Introduction to SNMP
An agent responds to a request by sending a single command, the
GetResponse command. This command contains the requested
information.
A manager changes information (variables) in the agent by sending a
single command, the SetRequest command. This command is used to
manipulate management data.
A trap is used by an agent to report extraordinary events. Refer to
Traps and Their Purpose on page 1-5.
Figure 1-1 SNMP Commands and Responses
Why Variables Exist
In a Managed
Device
Variables are the means by which a switch or director (and other
devices) keep track of their performance, control their own
performance, and provide access to their performance for 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 (Objects)
in a Managed
Device
An agent is the entity that interfaces to the actual object being
managed (Figure 1-2 on page 1-4). The agent understands the
language of SNMP and translates between the manager and the
object. Objects may be retrieved and/or modified by the manager,
and it is the agent’s job to return the requested object’s value. Within
the agent is at least one, maybe several, collections of definitions
Ge
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Get Values
NMS Switch
Se
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S
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Set Values
GetR
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GetNextR
equest PDU
Get Next Values
NMS Switch
Tr
ap P
DU
Send Trap