Simple Network Management Protocol (SNMP) Object identifiers (OIDs) for non-existing environmental monitors - IBM Server
RETAIN tip: H21192
Using Simple Network Management Protocol (SNMP) to get temperature and humidity parameters from an IBM 1U 9 C19/3 C13 Switched and Monitored Distributed Power Interconnect (DPI) Power Distribution Unit (PDU), Option part number 46M4002, always will return a value of either '0,' or a null string.
(Note: DPI = Distributed Power Interconnect)This applies for the last reading of temperature and humidity, in addition to the buffer to hold a trend history of temperature and humidity values.
Either using specific SNMP 'get' commands to the affected parameters, or an SNMP "walk" to get all Object Identifiers (OIDs) defined in the Power Distribution Unit (PDU) Management Information Base (MIB) file will result both in the return values of '0' or a null string.
This is because there is no existing hardware within the PDU itself to implement these environmental parameters.
Note: There is an optional PDU Environmental Monitor Probe (EMP) that can be connected to the PDU and this EMP does provide an alternate set of environmental parameters (with their own unique MIB OIDs) that may be read by way of SNMP to return proper temperature and humidity values.
The system is configured with one or more of the following IBM Options:
This tip is not system specific.
This tip is not software specific.
The affected Power Distribution Units (PDUs) do not have integrated hardware monitors for environmental temperature or humidity. An optional Environmental Monitor Probe (EMP) is available that connects to the PDU with a standard Ethernet cable and RJ45 connector.
This optional EMP (Option part number 46M5367, replacement part number(CRU) 46M5368) provides temperature and humidity parameters that may be read from the PDU with Simple Network Management Protocol (SNMP). The EMP temperature and humidity parameters are defined by a separate set of Object identifiers (OIDs) in the PDU Management Information Base (MIB) file, unique from the PDU internal OIDs for temperature and humidity.
The change history for PDU firmware version V01.2_1 includes a description of additions to the PDU MIB file, including OIDs 'ibmPduThermalLastReading' and 'ibmPduHumidityLastReading.'
This may lead users to believe they can read these OIDs from the PDU using SNMP. Although these parameters exist in the MIB file, the underlying hardware does not exist in the PDU.
There are additional OIDs in the MIB file that do not exist in the PDU hardware, including 'ibmPduThermalBuffer' and 'ibmPduHumidityBuffer.' A read of any of these OIDs will return a value of either '0' or a null string.
If the MIB OID is an integer type, then the returned value will be '0.' If the MIB OID is a string type, then the returned value will be a null string. Any MIB OID with 'Buffer' in the name is a string type. The other MIB OIDs are integer type.
All EMP environmental OIDs in the PDU MIB file have the common prefix 'ibmPduExt' in their name. These are valid OIDs to read with SNMP. The non-existing environmental OIDs in the PDU MIB file have the common prefix 'ibmPdu' in their name, without the 'Ext' part.
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Document id: MIGR-5092906