DPS Telecom D-PK-NGAAR, User Manual, Page: 48 / 80

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How traps Set and Clear each of the 32 SNMP Alarm states
Based on the rules you specify here, 32 virtual "SNMP Alarms" within the NetGuardian's alarm space will be
controlled by the receipt of traps that match OIDs and (optional) Variable Bindings that you specify. Each of the
32 SNMP alarms monitors for two different inbound traps: Set and Clear. When either of these is received, the
alarm state is set/cleared accordingly.
How to handle traps from devices that Set but never Clear
Some SNMP devices may not report Clear conditions with traps. They merely send a Set trap, then send that
same Set trap again later if the condition occurs again. This would ordinarily present a problem for your
NetGuardian. The SNMP Alarm would Set after the first trap was received, but then would remain Set forever.
You would constantly see an Alarm state, and future Set traps would not trigger notifications because the state
would not be changing from Clear to Alarm.
Fortunately, your NetGuardian was designed with this common problem in mind. For devices that send Set traps
but never send Clear traps, simply specify exactly the same values for the Clear trap as you did for the Set trap.
When the Set trap is received, it will match both the Set condition and the Clear condition. Because of the order in
which the conditions are evaluated, this will cause your SNMP Alarm to Set for a split-second before Clearing.
This is long enough to trigger any applicable Notifications for this alarm event.
Because the alarm state is immediately Cleared, this SNMP Alarm point is once again ready to receive another
Set trap in the future.
SNMP Alarms Settings
Id
The SNMP Alarm point number
Description
User-editable description for this SNMP Alarm
1-8 (Notifications)
Check these boxes to send alert notifications for this alarm point using
Notification Device(s) 1-8.
Advanced SNMP Alarms Settings (Click "Details>>")
Enterprise (v1) /
TrapOID (v2)
Enterprise OID (if receiving SNMPv1 trap) or Trap OID (if receiving SNMPv2c
trap)
Generic (v1) Generic Trap number for SNMP v1 traps only (ignored if v2 trap received)
Specific (v1) Specific Trap number for SNMPv1 traps only (ignored if v2 trap received)
Variable Binding
(optional) Additional OID to uniquely identify a particular variable binding that will be
required within this SNMP trap. A trap that is lacking the specified variable binding
will not match and will not trigger Alarm/Clear. The variable bindings available in the
dropdown menu are specified in Provisioning > Variable Bindings, allowing you to
conveniently reuse common variable bindings without typing them in each time.
Value Contains
(required when Variable Binding is used) Value that must be contained within the
variable binding value. Must be an integer or a string. To require that the specified
variable binding exists in the trap but to match on any value, use "*" in this field.