[Nut-upsdev] SNMP on HP UPS

Philip Ward p.g.ward at stir.ac.uk
Wed Mar 18 11:11:47 UTC 2009

We use HP R5500XR UPS, and they all have SNMP cards. These devices
supposedly use the IETF MIB, but in order to get the SNMP driver to talk
to them I have had to hack it slightly.

I'd like to see these UPS proplerly supported in the official nut
release (mostly so I don't have to faff around patching and repackaging
when a new version comes out) and would be more than happy to provide
patches, but I'd like to see if anyone has an opinion regarding these
fixes. Simply changing ietfmib.h (which is all I have had to do to get
it to work) would probably break it for other SNMP UPS. I can see a
couple of ways to fix this.

One way would be to add a new mib (e.g. hpmib.h). This would be the
simplest, but adds extra maintenance.

A more complicated way would be to make the snmp driver a little more
Currently it chokes when an expected oid is not available on the device
with which it is communicating. (For example ietfmib.h specifies
batt.current at oid Our R5500XRs don't have
provide this oid so the snmp driver complains and dies.) It may be
better if it ignored absent oids.

Also the expected data is not always in exactly the same place. For
example the IETF MIB specification states that output voltage should be
at oid
ietfmib.h is written to get this data from oid
Our R5500XRs provide the data at oid
Should the SNMP driver be told to find the data at and then automatically drill down further?

I have attached a unified diff showing what had to change in ietfmib.h
to get the driver to work. I can document the changes in greater detail
if required.

Philip Ward
Unix Systems Administrator
Ext 7274

Academic Excellence at the Heart of Scotland.
The University of Stirling is a charity registered in Scotland, 
 number SC 011159.

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