Snmp Mib Objects - 3Com VCX V7122 User Manual

can be determined via SNMP without the overhead associated with logging into the
device, or establishing a Transmission Control Protocol (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 an operant 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.
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 a 'trap' message) to notify or alert 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 above message types are all encoded into messages referred to as Protocol Data Units
(PDUs) that are interchanged between SNMP devices.

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, these branches are usually devoid of any meaningful data or objects.
The 'tree' structure described above is an integral part of the SNMP standard, though 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.
Table MIB Objects - Contain multiple sections of management data. These objects are
distinguished from 'Discrete' items (above) by requiring a '.' (dot) extension to their
names that uniquely distinguishes the particular value being referenced. The '.' (dot)
extension is the 'instance' number of an SNMP object. For 'Discrete' objects, this
instance number is zero. For 'Table' objects, this instance number is the index into the
SNMP table. SNMP tables are special types of SNMP objects which allow parallel arrays
of information to be supported. Tables are distinguished from scalar objects, so that
tables can grow without bounds. For example, SNMP defines the 'ifDescr' object (as a
standard SNMP object) that indicates the text description of each interface supported by
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