Getting Temperature Data from a 6500 via SNMP

I apologize to my adoring fans (both of you) for the lack of posting.  I’m in the middle of moving, buying a new house, selling my current house, getting a mortgage, etc.  I’ve up until 11:30 nearly every night filling out forms and going through red tape.  Don’t get me started on getting money from a 401k!  Anyway…

I got in this morning, and a coworker was telling me that the data center’s HVAC was crippled due to an oil leak, and it was 90F in there.  D’oh!  It wasn’t quite that high, but it was warm.  Luckily, all of our network gear is on the end of the rows with AC, so we’re safe, but it got me thinking about monitoring temperature of our 6500s via SNMP.  I’ve done it via Cacti, but I never really looked how to do it manually.

I read this article on Cisco’s site which made it clear as mud.  Basically, you have to query the entPhysicalIndex OID branch to get an integer that represents the physical sensor, then you query the entSensorValue to get the temperature.  I made the lazy choice to use grep on entPhysicalDesc OID to find the module I wanted and use that to grep the entSensorValue for the temp.

Let’s say I’m looking for the outlet temperature (the temperature of the air on the way out) on module 3.  First, let’s find out what th entPhysicalIndex is by walking the entPhysicalDesc OID and grepping out “module 3”.

Since we’re looking for the outlet temperature, we can see the index in question is 3003.  Now, we use that to query the entSensorValue.

Ah…a cool 19C.

This is not a very graceful way to do it, but it gets the job done in a pinch.  I haven’t tested it, but I would imagine this technique would work on 7600s as well.  I know it doesn’t work on 2950s and the like.

Send any house keys questions my way.

Aaron Conaway

I shake my head around sometimes and see what falls out. That's what lands on these pages.

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6 comments for “Getting Temperature Data from a 6500 via SNMP

  1. August 19, 2009 at 3:53 pm

    I have used this in the past and it works OK. The only thing to note is that it will report at temperature of about 35 degrees Celsius. Which sounds a bit warm until you realise that it is the EXHAUST temperature of the hot air LEAVING the blade. Of course it will be hotter.

    The thing to monitor is the CHANGE in temperaute and set an alarm is the temperatute goes over, say, 45 degrees.

    Works a treat.

  2. October 7, 2009 at 8:37 am

    I have never worked on it but find a useful for my network.

  3. October 8, 2009 at 5:07 am

    I’m using this method on a 7609 and it works perfectly, except that I see a lot of outlet temperatures lower than the inlet temperatures! Now, this could either mean the chassis is actually cooling the air in some areas, or the sensors are lying. So the question is: Is it possible the chassis could be cooling the inlet air in some cases, resulting in a lower outlet temperature?

  4. October 8, 2009 at 8:36 am

    I’m not really sure if that’s possible, Archmangle. You would think that the temperature would at least be the same out as in. Perhaps you can ask the TAC?

  5. someone
    December 28, 2009 at 11:11 pm

    Hi.. Which OID should be put in MRTG config to monitor those temperature ?

  6. December 29, 2009 at 9:17 am

    Hi, someone. That depends on what you want to monitor. If you want to measure the temperature of the air on the way out, then measure the outlet temperature. If you want to measure the temperature difference like Etherealmind suggested (which is how much hotter the blade/module makes the air), you would take the outlet temperature, subtract the inlet temperature, and graph the difference.

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