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If the object with a specified OID address does not exist, the SNMP agent returns an error code with a different OID address (because the object with the required OID does not exist) and therefore the communication will be denoted as unsuccessful. The I/O tag passes to the „Unknown value“ state. If it is necessary to indicate the line status by value change and not by the validity of the object's value, the object of DI type can be created, an integer value (e.g. UpTime) can be asked for and an automatic number to boolean conversion can be utilized, where 0 is converted to false and the other values to True. The I/O tag can be then configured to use a default value and to set the default to False. Then the object may acquire only the values True or False, depending on the object's availability in the SNMP agent.
The I/O tag with an address starting with %IGNORE will be ignored.
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Request: Default value Get causes the values to be read by a Get SNMP request.
Some devices have problems providing values by the Get request if the object is an item of an array. Then, you must configure the type of request GetNext and the address should be OID of the previous object (to find the address, use the Java application MIB Browser (http://tl1.ireasoning.com/mibbrowser.shtml) that reads the whole tree of values and detects the OID address of the previous object).
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