MonitorMagic - Tools4Ever.com

Using MonitorMagic
Next topic in sequence: Snmp get monitor - Formula calculation
See also:
MonitorMagic SNMP support
Snmp get monitor - Overview
Snmp get monitor - Tables
Snmp get monitor - Formula calculation
(This topic is part of a sequence of topics that start with Snmp get monitor - Tables
When collecting SNMP data, it is very well possible that you want to perform some data
calculation before you evaluate the rules. Example: Suppose you want to create a rule that
should be triggered if the average number of bytes received per second on an interface card
exceeds a threshold. This type of information is available from MIB-II, the interface table. Table
entry 1.3.6.1.2.1.2.2.1.10 (iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifInOctets)
identifies the total number of bytes received on each interface card. But, this is a cumulative value
that will increase in time only. By itself, this value will not show the average number of bytes
received per second. What we really need is the result of a formula that calculates the
difference of two samples of the cumulative value, divided by the time in seconds of these two
samples:
In formula:
ValueOld:The total number of bytes received at time Told.
ValueNew: The total number of bytes received at time Tnew:
Average number of bytes per second = (ValueNew - ValueOld) / (Tnew - Told)
MonitorMagic support a number of formulas by default. To specify the formula activate the
monitor policies window, select the policy, right click the mouse, and select the menu option
Add monitor, Snmp get. Press the Add button. You will be shown the Snmp object identifier
specification window. Press the Advanced button. The formula's can be selected from the
bottom list.
Formula's can be calculated over the first 2 object identifiers of the list Object identifier
specification only. These object identifiers are referred to as Oid1 and Oid2. For these object
identifiers, MonitorMagic also stores the previous value and elapsed time since the previous
value. Note that the result of the formula calculation can be stored in the database and can be
used for rule criteria evaluations.
Available formula's:
Standard (value of Oid1)
No formula calculated, result equals the value of the first object identifier.
Oid1 difference in time (ValueNew-ValueOld)
Result equals the difference between current and previous value of the first object identifier.
Oid1 change per second (Vnew-Vold)/(Elapsed time)
Rate calculation, the result is the change per second of the first object identifier in units per
second.
Oid2 difference in time (ValueNew-ValueOld)
Result equals the difference between current and previous value of the second object identifier.
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