Snmp Mib Objects - Nortel VoIP Gateway Configuration Manual

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SNMP MIB Objects

Each of the following message types fulfills a particular requirement of network managers:
• Get Request:
Specific values can be fetched via the "get" request to determine the performance and state of
the device. Typically, many different values and parameters can be determined via SNMP
without the overhead associated with logging into the device, or establishing a TCP
connection with the device.
• Get Next Request:
Enables the SNMP standard network managers to "walk" through all SNMP values of a device
(via the "get-next" request) to determine all names and values that the device supports. This is
accomplished by beginning with the first SNMP object to be fetched, fetching the next name
with a "get-next", and repeating this operation until an error is encountered (indicating that all
MIB object names have been "walked").
• Set Request:
The SNMP standard provides a method of effecting an action associated with a device (via the
"set" request) to accomplish activities such as disabling interfaces, disconnecting Users,
clearing registers, etc. This provides a way of configuring and controlling network devices via
SNMP.
• Trap Message:
The SNMP standard furnishes a mechanism by which devices can "reach out" to a network
manager on their own (via the "trap" message) to notify the manager of a problem with the
device. This typically requires each device on the network to be configured to issue SNMP
traps to one or more network devices that are awaiting these traps. The Trap messages are sent
to the SNMP Manager. The IP address of SNMP Manager is defined in the ini file or the
Network Settings screen on the web interface.
SNMP MIB Objects
The SNMP MIB is arranged in a tree-structured fashion, similar in many ways to a disk directory
structure of files. The top level SNMP branch begins with the ISO "internet" directory, which
contains four main branches:
• The "mgmt" SNMP branch contains the standard SNMP objects usually supported (at least in
part) by all network devices.
• The "private" SNMP branch contains those "extended" SNMP objects defined by network
equipment vendors.
• The "experimental" and "directory" SNMP branches, also defined within the "internet" root
directory, are usually devoid of any meaningful data or objects.
The "tree" structure described above is an integral part of the SNMP standard, however the most
pertinent parts of the tree are the "leaf" objects of the tree that provide actual management data
regarding the device. Generally, SNMP leaf objects can be partitioned into two similar but slightly
different types that reflect the organization of the tree structure:
• Discrete MIB Objects: Contain one precise piece of management data. These objects are
often distinguished from "Table" items (below) by adding a ".0" (dot-zero) extension to their
names. The operator must merely know the name of the object and no other information.
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