SNMP Agent Trap Send Rule Edit
SNMP Trap or Inform messages sent by this IoTServer are defined by rules outlined here. Traps may be sent as v1, v2c, or v3, and this selection is made in the SNMP Trap Destination Device configuration. The same trap may be sent to different devices as both v2c and v3 at the same time using the same Trap Send Rule.
Rule Number – Used as a reference in the rule list for ordering the rules.
Branch – Specifies which branch in the MIB that this trap rule applies to, and primarily provides the means to look up the local object number that should be evaluated.
Index – Specifies the index or row number in the given branch for looking up the local object nubmer.
Test – Defines the test that should be performed to determine if the trap send rule state is true or false. Trap state is considered “true” when this condition is met
|Test label||Test performed on object versus threshold|
|GT||Object greater than threshold|
|GE||Object greater than or equal threshold|
|LT||Object less than threshold|
|LE||Object is less than or equal threshold|
|EQ||Object is equal threshold|
|NE||Object is not equal threshold|
|DEV||Object deviates from threshold by hysteresis amount|
|DELTA||Object has changed by threshold amount|
For most tests, the object is simply compared to the threshold value. The delta test is a special case. The threshold specifies an amount by which the local object needs to change before the rule test will be flagged as true. However, this “true” state is only temporary. Once the trap is sent, the new object value is now saved for subsequent tests of “changed by”. Every time the local object changes by the threshold amount, a new trap will be sent.
Test type delta with threshold of zero is a special case within the special case. If the test type is delta and the threshold value is zero, then the trap will be sent any time the local object (found by looking it up in the MIB) has been updated or changed by some other action in the system, without any regard for what the actual value of the object is.
Threshold Value (CSV "CondVal") – Provided no threshold object number is given, this becomes the threshold value for test purposes.
Threshold Object (CSV "CondObj")– Overrides the threshold value when given (non-zero), and provides the local object from which a test threshold should be retrieved.
Hysteresis (CSV "Hyst") – Specifies the hysteresis value to be applied in the test process. Hysteresis is used to prevent a flood of trap messages when the object is hovering near the threshold but fluctuating frequently. For ‘greater than’ type tests, once the rule state becomes true, the object value must fall below the threshold by the hysteresis amount before the rule state will return to false. For ‘less than’ type tests, once the rule state becomes true, the object value must rise above the threshold by the hysteresis amount before the rule state will return to false. For example, if the rule threshold is 10, and the test is ‘greater than’, then the rule state will become true when the object value exceeds 10. If the hysteresis value is 2, then the object value must now fall below 8 before the rule state will return to false.
The hysteresis value takes on a special role when the test type is “deviates by”. The rule state will be true when the difference between object value and threshold exceeds the hysteresis amount in either direction, high or low.
SendOnTrue – Select (use Y/N in CSV) to enable the sending of a trap when the condition specified by this rule tests “true”.
SendOnFalse – Select (use Y/N in CSV) to enable the sending of a trap when the condition specified by this rule tests “false”.
Device Group – The device group allows selectively sending the same trap to multiple devices. Both the trap send rules and the trap devices have a group association. When the group association of a trap rule matches the groups that the device is a member of, the trap will be sent to that device, and all devices included in the group.
The group selection is made as a bit mask labeled "DevMask" in CSV and XML files. Group "A" is bit 0 or value of 1. Group "B" is bit 1 or value of 2. Group "C" is bit 2 or value of 4, and so on. The mask is the summation of the groups. Only the first 8 bits are used in the web UI for ease of use. Internally, the test for group membership is a simple logical AND of the mask values found in the trap rule and the device configuration.
SendInform – Uncheck box (default) to send the message as an SNMP Trap. Check box to send the message as an SNMP Inform. In the CSV or XML file, use "Y" to send as Inform, "N" to send as trap. If omitted, the default is to send an SNMP Trap.
OnTime – Specifies a minimum amount of time in seconds that the “true” state must exist before the trap state will be fully regarded as true and “true” trap sent. If the condition tests true, and within this time period returns to false, no “true” trap will be sent.
OffTime – Specifies the minimum amount of time in seconds that the “false” state must exist before the trap state will be fully regarded as false and the “false” trap sent. If the condition tests false, and within this time period returns to true, no “false” trap will be sent.
TrueMsg – Provides a user defined message that will be delivered as one of the varbinds in any “true” Trap or Inform message sent.
FalseMsg – Provides a user defined message that will be delivered as one of the varbinds in any “false” Trap or Inform message sent.
RepTrue – Used to repeat the trap this number of times when true. Traps are not acknowledged, so this provides a means of repeating the same Trap message to better ensure delivery. Set to -1 to repeat indefinitely while condition tests true.
RepFalse – Used to repeat the trap this number of times when false. Traps are not acknowledged, so this provides a means of repeating the same Trap message to better ensure delivery. Set to -1 to repeat indefinitely while condition tests false.
RepTime – Specifies the amount of time in seconds to wait in between repeated sending of the same Trap message as indicated by the repeat count attributes above.