Managers And Agents; Snmp Manager And Agent Communication - Cisco 4700M Administration Manual

Information About SNMP
This section contains the following topics:
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Managers and Agents

SNMP uses software entities called managers and agents to manage network devices:
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There are many different SNMP management applications, but they all perform the same basic task.
These applications allow SNMP managers to communicate with agents to monitor, configure, and
receive alerts from the network devices.The ACE supports traps and SNMP get requests but does not
support SNMP set requests to configure values on the device. You can use any SNMP-compatible NMS
to monitor the ACE.
In SNMP, each variable is referred to as a managed object. A managed object is anything that an agent
can access and report back to the NMS. All managed objects are contained in the MIB, which is a
database of the managed objects called MIB objects. Each MIB object controls one specific function,
such as counting how many bytes are transmitted through an agent's port. The MIB object consists of
MIB variables, which define the MIB object name, description, and default value.The ACE maintains a
database of values for each definition.
Browsing a MIB entails issuing an SNMP get request fromthe NMS. You can use any SNMPv3, MIB-II
compliant browser to receive SNMP traps and browse MIBs.

SNMP Manager and Agent Communication

The SNMP manager and the agent can communicate in several ways. The Protocol Data Unit (PDU) is
the message format that SNMP managers and agents use to send and receive information.
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Cisco 4700 Series Application Control Engine Appliance Administration Guide
7-2
Managers and Agents
SNMP Manager and Agent Communication
SNMP Traps and Informs
SNMPv3 CLI User Management and AAA Integration
CLI and SNMP User Synchronization
Multiple String Index Guidelines
Supported MIBs and Notifications
The manager monitors and controls all other SNMP-managed devices (network nodes) in the
network. At least one SNMP manager must be in a managed network. The manager is installed on
a workstation somewhere in the network.
An agent resides in a managed device (a network node). An agent is a specialized software module
that receives instructions from the SNMP manager and also sends management information back to
the SNMP manager as events occur. For example, an agent might report such data as the number of
bytes and packets in and out of the device or the number of broadcast messages sent and received.
The SNMP manager can perform the following operations:
Retrieve a value (a get operation) from an agent. The SNMP manager requests in formation from
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the agent, such as the number of users logged on to the agent device, or the status of a critical
process on that device. The agent gets the v alue of the requested MIB object and sends the value
back to the manager (a get-response operation). The variable binding (varbind) is a list of MIB
objects that allows a request recipient to see what the originator wants to know. Variable
bindings are object identifiers (OID)=value pairs that make it easy for the NMS to identify the
information that it needs when the recipient fills the request and sends back a response.
Chapter 7 Configuring SNMP
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