Who Is A Manager; Manager And Agent Relationship - Juniper SECURITY THREAT RESPONSE MANAGER 2008.2 - SNMP AGENT GUIDE REV 1 Manual

54 SNMP O
VERVIEW

Who Is a Manager?

Manager and Agent
Relationship
manager using SNMP. A management information exchange can be initiated by
the manager (through polling) or by the agent (through a trap). An Agent functions
as a device that gathers and sends data about the managed resource in response
to a request from a manager. UDP ports 161 and 162 are the default ports
reserved for SNMP.
The Agent monitors for requests and replies using port 161 and reports
asynchronous traps on port 162, unless configured to use different ports. SNMP
accommodates resources that do not implement the SNMP software using
proxies. A proxy is an SNMP agent that maintains information on behalf of one or
more non-SNMP devices.
A Manager manages one or more agents from a remote location. For example, if
your organization includes four office locations with more than 200 computers, 5
printers, and 3 system administrators. To manage these devices, the system
administrators must travel between the physical locations. However, if your
organization is using SNMP Managers, the system administrators can manage all
devices from their location. The system administrators can query the agent from
the Manager to determine the status of the device. If the Agent automatically
informs the Manager when a problem is about to occur (for example, the paper tray
in a printer includes less than 50 sheets of paper), then the system administrator
can make the necessary changes to prevent the problem from occurring.
SNMP facilitates communication between a managed device (a device with an
SNMP agent, for example, a router) and an SNMP Manager or management
application (represents a user of network management). The SNMP agent on the
managed device provides access to data (managed objects) stored on the
managed device. The SNMP manager or management application uses this
access to monitor and control the managed device.
Communication is processed using SNMP Protocol Data Units (PDUs) that are
typically encapsulated in UDP packets, and five kinds of operations are permitted
between managers and agents (managed device) including:
• The manager can perform a get (or read) to obtain information from the agent
about an attribute of a managed object.
The manager can perform a get-next to do the same for the next object in the
•
tree of objects on the managed device.
• The manager can perform a get-bulk to obtain information about a group of data
from the agent. This is not possible using SNMP V1.
The manager can perform a set (or write) to set the value of an attribute of a
•
managed object.
• The agent can send a trap, or asynchronous notification, to the manager
regarding an event on the managed device.
To specify to the SNMP agent which managed objects you wish to consider, the
SNMP manager or management application uses a well-defined naming syntax.
STRM SNMP Agent