Cisco 15327 - Manual (Page 370)

22-4
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 22 Configuring SNMP
SNMP Agent Functions
SNMP Agent Functions
The SNMP agent responds to SNMP manager requests as follows:
• Get a MIB variable—The SNMP agent begins this function in response to a request from the NMS.
The agent retrieves the value of the requested MIB variable and responds to the NMS with that value.
• Set a MIB variable—The SNMP agent begins this function in response to a message from the NMS.
The SNMP agent changes the value of the MIB variable to the value requested by the NMS.
The SNMP agent also sends unsolicited trap messages to notify an NMS that a significant event has
occurred on the agent. Examples of trap conditions include, but are not limited to, when a port or module
goes up or down, when spanning-tree topology changes occur, and when authentication failures occur.
SNMP Community Strings
SNMP community strings authenticate access to MIB objects and function as embedded passwords. In
order for the NMS to access the ML-Series card, the community string definitions on the NMS must
match at least one of the three community string definitions on the ML-Series card.
A community string can have one of these attributes:
• Read-only (RO)—Gives read access to authorized management stations to all objects in the MIB
except the community strings, but does not allow write access
• Read-write (RW)—Gives read and write access to authorized management stations to all objects in
the MIB, but does not allow access to the community strings
• Read-write-all—Gives read and write access to authorized management stations to all objects in the
MIB, including the community strings
Using SNMP to Access MIB Variables
An example of an NMS is the CiscoWorks network management software. CiscoWorks software uses
the ML-Series card MIB variables to set device variables and to poll devices on the network for specific
information. The results of a poll can be displayed as a graph and analyzed to troubleshoot problems,
increase network performance, verify the configuration of devices, monitor traffic loads, and more.
As shown in Figure 22-2 , the SNMP agent gathers data from the MIB. The agent can send traps, or
notification of certain events, to the SNMP manager, which receives and processes the traps. Traps alert
the SNMP manager to a condition on the network such as improper user authentication, restarts, link
status (up or down), MAC address tracking, and so forth. The SNMP agent also responds to MIB-related
queries sent by the SNMP manager in get-request, get-next-request, and set-request format.
Figure 22-2 SNMP Network
get, get-next, get-bulk
Network device
get-response, traps
32632
SNMP Manager
NMS
MIB
SNMP Agent