ASR9k Power Module Error (PM_NO_INPUT_B_DETECTED).

[n.t85]

Hi Community,

I have a question for ASR9k power supply redundancy. 

The following error is logged Power Module Error (PM_NO_INPUT_B_DETECTED). Is there any issues with the normal operation in case the chassis will start to work with load (At the moment there is only one RSP card working)

Also in case the DC power supplies are installed both on the same power shelf, are the power supplies at least redundant to each other in case one of them fails?

Thanks in advance,

Regards  

[smilstea · Accepted solution]

You can check admin show environment power to see the redundant states and power capabilities.

This error is meaning power from input B is not seen, input A is likely ok though, if there is a failure on input A then you would see a reduction in the amount of available power.

Also note that the power shelves work in a pool of power to provide power to every component in the system, so if you lost a shelf then the load would go up on the other shelf.

Sam

[Aleksandar Vidakovic]

hi Nikola,

The output of "admin show environment power-supply" shows the current status of power supplies but also the power budget. 

ASR9000 is a single power zone. All power supplies are feeding into that zone, regardless of which power shelf they are installed in. DC V2 provided for built-in redundancy for two feeds, but DC V3 provides nominal power when both feeds are connected. Look up BRKARC-2003 from Cisco Live Europe 2015 to find a more detailed explanation of DC V2 vs DC V3.

/Aleksandar

[n.t85]

Thanks for the reply,

So currently as I have two power supply modules installed on only one shelf, I am left only with redundancy at module level. Lets say one of the modules fails the one left would take all the load right?

Just one question though, if I require to upgrade to DC-V2 power supplies do I need also to upgrade the Shelfs?

Regards,

[Aleksandar Vidakovic · Accepted solution]

Both power modules are providing power simultaneously. So if one fails, there is nothing to "take over" strictly speaking. If the remaining power module can provide enough power to keep cards running, there will be no service impact. Note that power budget calculation takes into account the maximum power required by a card, not the actual.

[n.t85]

Yes Exactly what was showing when using the power calculator from Cisco.  

Thanks,