PI SNMP Interface. First of
all, before to go to the PI SNMP
Interface, you have to know what SNMP is.
SNMP stands for Simple Network Management
Protocol. This is a standard protocol
for multiple devices from
various vendors to provide performance information about
themselves. SNMP-enabled
devices contain an SNMP agent,
and we will query the agent
to get performance information. Many
hardware and software products do have SNMP
agents. The most popular ones are
probably network switches, routers, printers,
firewall, and so on. Even
operating systems such as Windows or
RDBMS's such Oracle, Informix
and more do have SNMP agents
on them. Just like for
Performance Counters in Windows, SNMP variables
can be accessed using a path.
In this case, we call this path OID,
Object IDentifier.
The Object IDentifier is a text string
represented in either decimal
or textual notation. It
starts with a period, and then drill down into
branches and sub-branches and sub-sub-branches.
An example of an OID
can be found in the Notes at the bottom of this page. You could
represent a counter in an SNMP agent
via its numerical notation, such as
this one: 1, 3, 6 and so on,
or via its textual representation.
These two are equivalent.
In order to make communication with
SNMP agents easier, we normally use what we
call MIBs. MIBs stand for Management
Information Base.
This a plain text file describing
the OID's, the counters that are
exposed by the SNMP agents.
They are simply built for aliasing purposes.
They are not necessary for data collection,
as you only need the OID, the numerical
notation, but, they are pretty useful for
you to be able to see the OID's
in their textual notation. These
MIB files can simply be downloaded from various websites
which we will talk about in a few pages.
There are three different types of
OIDs, three types of counters that, that
can be provided by SNMP agents: the read-only
counters; the read-write counters; and traps.
Traps are unsolicited messages
sent by the agent. These will be covered
in the next chapter. This Interface,
the PI SNMP Interface, can read
counters and will be able to write
to the devices as well. For
these counters, you must use a community
string. What we call a community string in the SNMP
language is simply a password.
So that means you may have to ask your IT Managers
for a password to query your SNMP
devices. Because devices
normally provided hundreds and thousands of counters,
you sometimes need help to determine appropriate
parameters to monitor on your devices.
You can find some more information of the companies' websites
as well as SNMP reference sites such as
mibdepot which lists all the MIB Files -- can
be downloaded from almost all kind of devices.
And here is our PI SNMP Interface
which simply gathers information from
various SNMP agents on your network
and then archive this information into PI.
Obviously you have to make sure an SNMP
agent is installed and configured
on your data sources because, by
default, not all devices have their SNMP agent
available. Also, to
collect SNMP data from any Windows machine,
you will have to install the Windows SNMP
service. The procedure to do that can
be found in the Notes at the bottom of this page.
See, to install the SNMP service,
you can simply go in Add-Remove Programs
from your Control Panel.
On this window, you then choose Add-Remove
Windows Components. From
that one, in the list, you can choose
Management and Monitoring Tools.
And then if you click Details, you will have
the choice to install Simple Network
Management Protocol. From there,
when you click OK, Next and Finish,
the service is installed.
You then simply start the service using the
Services Window found under Administrative
Tools in your Control Panel.
Doing so will allow you to use
the PI SNMP Interface to query the agent
installed on Windows machines.
There are several parameters that are specific to the PI SNMP
Interface and that will work in conjunction with the plug-in
to configure tags that we will talk about in a couple of
pages. For example, in the plug-in,
you will be able to tell the Interface to regroup tags.
When you regroup tags in ICU,
here, you can set the maximum number of
tags per set -- by default, five.
To change this default, you can simply check
this box and enter your own number.
You could also change the maximum time allowed
per, per query, which is three seconds.
The time-out can be changed by checking this box
and changing the number here. In addition
to the time-out, you can tell the SNMP Interface to
retry calls that fail that number of time.
The check-box here and the
number here. In the next pages, you
will see about tag configuration. You will
see that in a tag you normally configure the password
to communicate with the SNMP agent. To omit
the password in the configuration for security purposes,
you can tell the Interface to use a password file.
You could check the check-box here and
edit the PI SNMP.PWD
file. This would tell the Interface, you go
in the Password file and read the passwords rather
than read them into the tag's configuration.
And another important parameter here
is the Allow SNMP "set."
This is to allow the Interface to perform
write operations to SNMP agents.