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SNMP
– Interface description
SNMP (Simple Network Management Protocol) is a protocol designed for
exchanging basic system information using short packets sent over UDP/IP.
Individual variables are described in a MIB (Management Information Base)
table that pertains to a particular device. The MIB is distributed as a separate
.mib file. For Poseidon products, the MIB is available on the supplied CD and
at our website.
SNMP is an asynchronous protocol based on the client/server model (SNMP Client / SNMP Agent in
this case). This means that a monitoring center (SNMP Client) requests the states of individual
variables, and the SNMP Agent implemented in the device responds.
SNMP support is implemented in many languages designed for creating dynamic websites (PHP,
ASP, Java, Perl, Python, and so on). Thanks to available modules, read and write access to data
provided by a device over SNMP is relatively quick to implement.
In the standard communication mode, a “request and response” communication model is used.
Variables are defined by a hierarchy (sequence) of numbers that is described in the MIB table, where
the meanings, names and formats of individual variables are given. If you know the hierarchy
(numeric line
– for example „.1.3.6.1.4.1.21796.3.3.1.1.2.3“ – Binary 3 input state) for the specific
value, MIB table is not needed.
For clarity, the following terms need to be understood:
MIB table
– The .mib file is a text file that describes individual variables supported by the
device. It contains the addresses, names, descriptions and numeric formats of the variables.
OID
is a variable identifier in the table. It is the “long” number that defines the position of the
variable in the tree of variables.
Some programs for working with SNMP do not support MIB files. In this case, you need to enter the
OID strings manually. These strings can be found in the MIB table. However, to save you some time
in first experiments with SNMP, a list of several variables with their OIDs follows:
